An Exchange in Locard’s Own Words (Part 6)

Translated by Kathleen Brahney
Commissioned by McCrone Associates, Inc.

Edmond Locard
Doctor of Medicine, Professor of Law, Director of the Lyon Laboratory of Police Techniques,
Vice-President of the International Academy of Criminology

Manual of Police Techniques
Third Edition, Completely Revised and Augmented.
Paris: Payot, 16 Boulevard St. Germain, 1939

Part VI-Other Stains, Microchemistry and Starches

Chapter IV


On the clothing of the suspect or at the scene of a crime, one may encounter diverse stains that could be confused with semen or pus, but which are produced by digested food.  Microscopic examination will allow one to discover:

  1. Debris from meat:
    Muscle fibers, elastic fibers, conjunctive tissue.
  2. Debris from vegetables:
    Grains of raw or processed starch; various plant cells (polyhedral, spherical, spindle-shaped, star-shaped, aligned in rows); vegetable fibers/hairs; spores.
  3. Fats:
    Containing many types of acids—butyric, caproic, caprylic, capric, palmitic, margaric, stearic, oleic—which can be distinguished by their points of fusion and by lecithins, with which one can determine the acids.  All of these stains are soluble in ether.
  4. Sugar:
    One can find sucrose or glucose. Only the latter will reduce Fehling’s liqueur and will turn alkalis yellow.

In general, albuminoid material can be recognized in the following reactions:

  1. The Biuret reaction:
    To an aqueous solution of the stain one adds two or three drops of copper sulfate and a little bit of potassium.  One will obtain a color that varies, according to the nature of the albumin, from pure violet to red-violet.
  2.  The xantho-protein [sic] reaction:
    Azotic acid [nitric acid] gives a yellow coloration that darkens in the presence of ammonia.
  3.  Adamkiewics’ reaction:
    The stain dissolved in crystallizable acetic acid takes on a slightly fluorescent violet tinge in concentrated sulfuric acid.


These present themselves as brilliant white plates that are often tear-shaped.  The difficulty is to not confuse them with grease stains. Confusion with semen, mucus or pus, however, is rarely possible.

Spots on clothing are removed by means of an extractor [solvent extraction].

Candle wax is formed in large part by stearic acid obtained by the saponification of fats and suets using lime.  Pure stearic acid is a solid white body, fusible at 68.38 degrees and soluble in alcohol and ether.  The candle, being composed of impure stearic acid—that is to say, not purified and still containing some fats—has a fusion point between 51 and 58 degrees C.  Its specific gravity is in the neighborhood of 0.850.

  1. Dosage of acidity:
    Scrape about 4 grams of the wax stain into a glass with about 70 cc of 95% neutral alcohol, dissolve it in a bain-marie and let it cool while shaking it. Add a few drops of phenolphthalein and titrate it with 0.5N KOH until there is a persistent pink color. The number of cc used, divided by 7.8, indicates the weight of the fatty acids in the stearic acid contained in the sample. Most of the time, the acid content thus obtained is between 95 and 99%.
  2. Fusion Point:
    The point of fusion can be obtained as follows:  Plunge a test tube containing mercury into a beaker containing oil. On the surface of the mercury, place a sample of the substance. Close the test tube with a cork that has a precision thermometer through it; the thermometer should plunge into the mercury. One heats this slightly with an alcohol lamp.  When the specimen melts, one notes the temperature. The fusion point should vary from 40 to 70 degrees C.
  3. Polarized Light:
    Franz Dangl of Vienna used a microscope equipped with a polarizing mechanism to analyze candle stains.  “All substances, such as wax, paraffin, stearine, ceresin, when placed between crossed Nicol prisms, illuminate the field of the polarizing mechanism as long as the substances are in a solid state.  But they will obscure the field when they enter into fusion, so that this important physical fact, from the point of view of fusion or solidification, makes it easy to define [the substance] even when there are only minimal traces of it.  Moreover, a very small layer of a melted sample—placed between the slide and the glass—will present perfectly typical structures in polarized light.  In order to avoid variations due to a more or less rapid degree of cooling, it is good to make strictly parallel preparations, and to raise the temperatures of the two samples simultaneously on the same heating plate, and then to let them cool down together, regularly and rapidly.  In this way, one can easily recognize their typical structures, which will be easy to differentiate in polarized light.”


Grease stains on clothing or linens may originate from food or from various other contacts.  One extracts them by means of an extractor. Identification can be carried out using the following methods:

  1. Iodine index (Hubl’s method):Prepare the five following liquids.
    1 — 25 grams of bisublimated iodine and 500 cc. of ethanol
    2 — 30 grams of HgCl2 and 500 cc. of ethanol
    3 — 24 grams 8 of Na2 S2O3, 5H2O, 1,000 grams of H2O; these are titrated
    4 — 10 grams of KI and 100 grams of H2O
    5 — 2% laundry starch

In an Erlenmeyer flask corked with emery (ground glass stopper), place about 0.3 grams of the substance to be tested.  Add 10 cc of chloroform to dissolve it, and 25 ml of a mix of liquids 1 and 2, in equal volumes.  Leave these in contact for 24 hours.  Titrate the excess iodine.  Introduce into the Erlenmeyer flask 30 cc of liquid 4 and 100 grams of water.  Put the titrated solution of number 3 in the presence of the laundry starch; wait for complete discoloration.

One will recognize the titrate of the iodo-mercuric solution; from the quantity of iodine obtained using the above method one will extract a number which, when adjusted for 100 grams of oil/grease, will be the iodine index.

  1. The Saponification Index (Koettstorfer‘s Index):
    This is the number of milligrams of potassium needed to soponify 1 gram of fatty material.In a 125-cc flask, place 3 to 4 grams of alcoholic potassium prepared as follows.  In 200 cc of pure alcohol, place 15 cc of 45% potassium washing powder; shake it hard; filter off the insoluble carbonates; titrate 25 cc of this solution by means of a liquid titrated with hydrochloric acid.Let it “digest” in an ascending refrigerant [reflux] for a quarter of an hour.  When the saponification has taken place, one titrates the excess potassium with hydrochloric acid.  The difference between the two titrates, in relation to 1 gram of fatty material, gives the saponification index.
  2. The Neutralization Index
    This is the number of milligrams of potassium needed to neutralize the free fatty acids contained in one gram of fatty material.  If the fatty material is liquid, the operation should be carried out cold; if the material is solid, the operation should be carried out using heat.

    Place 5 to 10 grams of fatty material in 50 cc of 95% alcohol.  Shake it and titrate the 0.10 N potassium hydroxide with phenolphthalein.


(This portion is thanks to Mr. Gaston Dumarchey, an assistant in the Police Lab of Lyon)

In the course of the criminal act—theft or murder, for example—the guilty party may rub against walls; his clothing will then bear a trace of the paint in the form of a stain or powder.  Or the person responsible for an auto accident may leave traces of paint from his vehicle on the victim or at the scene of the crime.  One can then compare these stains or powders taken with scrapings taken from the crime scene or the suspect’s automobile.

The constituents one will have to identify fall into two categories:

  1.  The base or support for the paint, which will be the only element in the case of untinted paint or varnish;

  2.  The colored or white pigments which give the paint its covering capacity.
    a. The support/base.  One must distinguish:

      1. Ordinary paints containing siccative [drying] oils—linseed oil or oil of Chinese wood [sic.]These are characterized by their solubility in mineral essence, essence of turpentine and ether, and by the iodine index determined from the last solution, in cases where the paint is new.  If the paints are not new, they remain insoluble in organic solvents such as ether, essence, alcohol, ether salts.  They will be soluble in concentrated solutions of caustic soda.
      2. Cellulosic paints, with a base either of nitrocellulose or cellulose acetate and an important number of natural or synthetic resins.A common characteristic of these paints is their permanent solubility in organic solvents (ether and alcohol) in the case of nitrocellulose, and for acetate, in mixtures of 60 – 40% alcohol and the acetates of methyl, butyl and amyl.Nitrate of cellulose will be further differentiated by the characteristic reaction of the nitric group, by means of the brucine [2,3-dimethoxystrychnine] reactive:  On a bit of the paint one places a drop of 0.3 grams of brucine in 100 cc of pure concentrated sulfuric acid.  In the presence of the nitric group, a red coloration will form, which changes to orange, than to yellow gold and then to greenish yellow.

b. Pigments In paints

One uses either natural mineral or synthetic pigments (either white or colored) or colored pigments that are obtained by coloring a white mineral with organic colorants.  The latter are generally in a solution of the solvents used in the determinations described above, and will be characteristic in those solutions.

In contrast, insoluble mineral pigments will be separated in those solutions through filtration and determined through the characteristic reactions of mineral analysis.

    1. Ceruse or hydrocarbonate of lead (2 CO3Pb + Pb(OH)2  Solubilize in HNO3, extend and titrate with H2S; black participate of lead sulfide, PbS.
    2. Silver white.  Sulfate of lead, Pb SO4. Solubilize with boiling ammonium acetate and treat with KI; yellow precipitate of lead iodide PbI3.
    3. Zinc white.  Zinc Oxide, ZnO.  Dissolve in HCl, extend, neutralize with NaOH, acidify with acetic acid, treat with H2S; a white precipitate of zinc sulfide, ZnS.
    4. Lithopone.  Sulfur of Zinc and sulfate of barite ZnS, BaSO4. Dissolve in hot H NO3, extend with water, filter.  Zinc is characterized in the filtrated material as above.  Dry the filter, scrape off a bit and place it in a test tube with pure, concentrated sulfuric acid; the sulfate of barite will dissolve.Fixed White.  Sulfate of barite, BaSO4.  Characterize it as described above.
  2. BLUES
    1. Prussian Blue, ferric ferrocyanide ((FeCy6)3 Fe4). Solubilize in acetic acid. [Cy is abbreviation for cyanide, CN]
    2. Berlin Blue.  This is Prussian Blue with mineral materials.  It will be easy to characterize using the preceding and following properties.
    3. Turnbull’s Blue,  Fe2Cy12Fe3.  Treat it heated with washing soda and potassium; this will produce ferrocyanide and iron oxide. With acetic acid the ferrocyanide will dissolve and the iron oxide will be characterized by its analytical properties.
    4. Mountain Blue.  Carbonate of copper hydrate Cu2CO3 (OH)or azurite.
    Schweinfurt’s green, Mitis green, Neuvied’s green, imperial green, Paris green, etc.  These are aceto-arseniates of copper mixed with plaster, sulfate, barite and lead sulfate.  When treated with NH3, they dissolve partially.  When heated in a test tube, they give off a nauseous odor.
    1. Chrome yellow, lead yellow, chromates and dichromates of lead.  Treat with HCl, reduce the chromate with C2H5OH, let it cool, add pure alcohol again to precipitate PbCl3 which one will collect on a filter. Dissolve it in HNO3 and treat it with H2S, yielding precipitate of lead sulfur, PbS.  In the filtered material, one will characterize the chrome with NH3; one will obtain a greenish blue precipitate of the hydrate Cr2(OH)3.
    2. Minium(Red Lead)  Saline oxide of lead, Pb3O4.  Dissolve in HNOand characterize the lead as described previously.
    3. Vermillion, or Cinnabar:  Mercuric sulfide, HgS.  Treat with royal water [sic. “eau regale“], extend, add K2Cr2O7, note a
      bright red precipitate of mercury dichromate.
    Ochres vary in color from yellow to red.  They consist of clays containing varying amounts of iron hydrates or oxides.  Characterize the iron by the reaction of Prussian blue with potassium ferro-cyanide over a solution of HCl and in the presence of a little nitric acid.
    1. Aluminum Powder:  Under a microscope, this has a characteristic metallic aspect.  Dissolve it in hydrochloric acid, noting the formation of hydrogen. If you add ammonia to the solution you have obtained, a flaky precipitate of aluminum hydrate will form.
    2. Bronze Powders:  Metallic aspect.  It dissolved in acids, yielding hydrogen.  One can then characterize and dose the constituent variables of the solution obtained—copper, aluminum, zinc.


(See Jacques Locard, “Contribution to the Analysis of Colorant Stains,” in the International Review of Criminalistics, 1937, no. 7) 

The first operation to be carried out with relation to colorants is to put the colorant into solution.  The method used by Soxhlet and Kumara (reduction and extraction with an extraction apparatus) gives good results.  Jacques Locard had Mr. Pignat construct an apparatus with the following characteristics:  A 20 cc flask, 12 centimeters high equipped with a 2.5 cm. neck.  Inside the neck is a case or cartridge with a 5cc capacity equipped with a siphon, which is destined to receive the material to be analyzed.  Above the flask is affixed, using an emery gear, a cooling mechanism, of the type used by Vigreux, 15 to 20 cm. high.

Using the apparatus is quite easy.  In the flask, place 15 cc of the solvent that you wish to use; generally this is distilled water or 95 degree ethyl alcohol.  The sample of the cloth to be examined is placed on the cartridge above the liquid.  Then put the cooling mechanism on top.  Heat the flask to a light boil; the steam condenses in the cooler.  The condensed liquid will fall, drop by drop, onto the material to be analyzed.  Little by little, the level of the liquid in the cartridge rises, and when it reaches the level of the siphon, the liquidthrough the siphoning actionwill all pass into the flask, taking with it a portion of the colorant.  The draining will stop at that point and the cartridge will begin to fill up again, until one obtains a second siphoning.  The liquid in the flask will gradually become enriched with the colorant, whereas the material to be analyzed, always in contact with the pure solvent, will see its coloration diminish with each siphoning.  After four hours, one can consider the process over.  If the stain is small, a 15 cc solution will be too diluted.  It can be concentrated by boiling it down to 5 cc, or even less if that is needed to obtain a fresh coloration. The solution thus obtained will then lend itself to physical examination.

    1. Color Comparison
      The incriminating solution and that of the control may present colorations that are so different that one will be able to conclude that further examination is not necessary.  If, on the contrary, the nuances are the same or are very close, further comparison can be carried out as follows.Choose two identical test tubes.  In one, place the incriminating solution; in the other, place the solution for comparison, which one has concentrated until it is slightly darker than the other solution.  Then add distilled water, one drop at a time and see if—at a certain moment—one can get exactly the same shade.
    2. Examination under Ultra-Violet Light
      A Woods lamp will be of the best service in differentiating the colorants.  Certain colorants, which might be confused in daylight, give entirely different fluorescences under a Woods lamp. Thus, under UV light, one obtains the following colorations:

      1. Yellow colors
        Primuline Yellow:  intense violet white
        Brilliant Flavine acid 5 J:  dark yellow
        Auramine O:  black with yellow highlights
        Naphthol Yellow OS:  black
      2. Red-Orange Colors
        Eosine:  light greenish yellow
        Metalline Yellow:  black
        Orange 2 Organol [sic]:  black
      3. Carmine Colors
        Rhodamine: A very bright orange
        Cerasine [sic]: dirty green
        Congo Red: dark brown
        Fuchsin [sic] acid: dull black
      4. Brown Colors
        Phosphine R: Bright yellow
        Phenyl Brown S: Dull black
    3. Spectroscopic Examination
      Spectroscopic determination of colorants demands a degree of purity that one does not usually find in commercial colorants.  In addition, it is not possible to subject the very small samples obtained to further purification.  Thus, the identification of a colorant by its spectrum gives only illusory results.In contrast, spectroscopic comparison of an incriminating stain and a comparablecolorant can yield indications that are very useful if one examines two samples simultaneously in the two containers of a microscope.  The apparatus used [i.e., in the Police Lab of Lyon] is an ordinary microscope equipped with a Leitz ocular spectroscope.  A few tenths of a cubic centimeter of the incriminating solution is sufficient when it is placed in a holder under the lens, whereas an appropriate solution of the colorant to be used for comparison is placed in the lateral tube.


Wet the stain with diluted hydrochloric acid; remove a bit and mount it on a slide; add a drop of 5% potassium ferrocyanide.  Ferric ferrocyanide will form:

4 FeCl3 + 3 (FeCy6)K4 =  12 KCl + (FeCy6)3Fe

This flaky Prussian blue precipitate can easily be seen with a microscope with an enlargement weaker than 200.  If the reaction is not a success, one can try
again, this time putting a drop of ammonia on before the ferrocyanide because if the reaction is too acidic, the ferrocyanide will decompose.

This method is applicable for rust stains on clothing, linens, etc.  But if the stain is on iron or on an iron alloy (such as a knife, etc.), the reaction will always be positive and one cannot use it except in cases where the stain is voluminous and dried, so that one can remove a bit that has not been in direct contact with the metal.  In any case, it is always better to use spectroscopic analysis.


In a great number of criminal trials, the identification of mud stains, supplemented by an analysis of dust is useful in determining where a suspect has been just prior to the time of his arrest.  Sometimes these analyses can verify the suspect’s alibi.  If, for example, the suspect claims to have spent the previous night in a particular location, an examination of his shoes and clothing can determine whether or not the individual passed through routes or streets that have left evidence of dirt that is different from that of the itinerary he claims to have taken.


The first priority is to act fast.  Mud stains only yield decisive results if they are taken the very instant the suspect is taken into custody. The magistrates, inspectors or gendarmes, armed with prior documentation, must seize the evidence right away.  The best thing to do is to seize the suspect’s shoes and clothing.  Only in cases where seizing these items proves to be impossible should one resort to scraping samples with a knife or gathering dust samples with a brush.  If such samples are taken in a police lab, it is best to remove the dried mud in successive layers, noting the order of the layers and numbering the samples.  The individual may, in effect, be carrying traces of various terrains.


First, one will describe the microscopic aspects of the various layers.  For each layer, one will then proceed as follows:

  1. Microscopic Examination. In a series of preparations, one will research the various crystals in the samples and set up a system.  One will note the degree of frequency of the various types in order to be able to differentiate those which determine the types of dirt and those that are accidentally present.  It is possible to have scrapings that do not contain any crystals at all, or they may not be determinable because of their small size.
  2. Microchemical Analysis. Treat the dried mud or mud powder with concentrated hydrochloric acid, in the presence of lead, in a bain-marie.  Renew these treatments until the disaggregate process is almost complete.  Then evaporate it until dry.  Bring it back with boiling distilled water, still in the bain-marie.  Filter it: the silicates will remain on the filter.  Evaporate the filtration to a very strong reduction.  Acidify it slightly with a few drops of hydrochloric acid.  Characterize the elements using the following microscopic reactions:
  • ALUMINUM. This metal will be characterized by alum of Cesium (chloride of Ce in one drop of the solution).  Octahedrons and cubo-octahedrons; if the solution is too concentrated with Al salt, dendrites (tree shapes or arborizations) will form, which, through dilution, will yield octahedrons.
  • ANTIMONY. This metal will be characterized by pyro-antimonite of Na: flat, round crystals often grouped in threes, prismatic rods.
  • CLAY (ARGILE). This is characterized by Morin’s solution, which allows one to recognize 1/600th of a milligram of clay per cubic centimeter, and gives a green fluorescence.  It absorbs a decoction of campeche wood [Tr. Genus haemotoxylon] and then becomes dark violet.
  • ARSENIC. This metal is characterized by silver arsenite (a small quantity of ammonia added to a mixture of arsenious acid and silver nitrate.)  Rhombuses and yellow pointed needles of sulfur.
  • BARIUM. This metal is characterized by barium sulfate (dissolved in heat in concentrated sulfuric acid.)  Small rectangular “tablets,” sometime with convex edges toward the exterior.  If the solution is saturated, one sees x-shaped skeletons.
  • CADMIUM. One forms an oxalate of cadmium, using oxalic acid as a reactive.  It is necessary that the addition of this acid, in cold temperatures, yields a crooked line. Heat it, and through cooling one obtains rhombuses and clino-rhombic prisms that are sometimes very long.  Some have hollow ends and resemble crystals of lead chloride.
  • CALCIUM. This metal will be characterized by calcium oxalate (oxalic acid in a very extended solution); when cold, one sees octahedrons, and star-shaped skeletons with 4 to 8 branches will appear; prisms are often forked on the ends and look like x-shaped skeletons.  In heat, tables and short clino-rhombic prisms with two spots, one consisting of two crystals at the base, the other of four crystals—two at the base and two on a face perpendicular to the base.The oxalates, obtained cold or hot, when treated with extended sulfuric acid in half its volume of water, yield gypsum crystals.
  • CARBONATES. These salts will be characterized by calcium carbonate, first in circular and spherical forms, then rhombohedrons with rounded contours.  Heated, one will find, in addition, branched and prismatic forms belonging to the ortho-rhombic carbonate.
  • CARBON/COAL. Carbon/coal shines with a metallic sparkle.  In carbon dust, one will note fragments with sharp spikes and brilliant surfaces.  It is indifferent to acids and alkalis, but it is combustible.  Bituminous coal is dull black, with rings and stripes as seen in the surface of wood, from which this substance originates.
  • CHLORINE. This metalloid will be characterized by lead chloride (see lead.)
  • COBALT. This is characterized by purpureo-cobaltic [sic] chloride.  One uses ammonia to act on the solution in a test tube.  One must use enough to make all the precipitates disappear; then one adds potassium permanganate, being careful not to put in too much.  Use only enough to turn the solution a pink color.  After cooling, neutralize it with a light excess of hydrochloric acid.  Bring it to a boil again and keep it at that point until the disaggregation of the chlorine is complete.  If the solution is not clear or if it is brown, it is because the quantity of hydrochloric acid is insufficient.  One must continue to add a few drops and keep it heated.  If, on the contrary, the solution is blue, it is because there is far too much hydrochloric acid.  If the solution contains enough cobalt, one obtains a violet purple crystalline powder.  Microscopic examination yields ortho-rhombic octahedrons that are quite dichroic.
  • COKEA. Black, porous surface that, most often, shines slightly.  Indifferent to reactive and scarcely combustible.
  • CHALK/LIME. Chalk is white and  is easily crumbled or crushed.  It effervesces in acids.
  • COPPERPresents a typical metallic color.  One can distinguish the following varieties according to the means of forming powder:(1) Powder from sharpening:  composed of very fine flakes that often adhere to the sharpening tool.(2) Powder from grinding or turning gives forms that are more precise than those of iron. There will be forms that are more or less bulging and striped.Copper will be characterized by ferrocyanide of copper ammoniac (one places a small fragment of ferrocyanide of K in a very diluted but strongly ammonic solution); through slow evaporation, rhombic table shapes and rectangular flakes with hoops and bundles of needles.  The crystals change from pale yellow to bright red brown as the ammonia evaporates.  Acetic acid gives an immediate color change due to the formation of copper ferrocyanide.
  • PEWTER. This metal is characterized by stannous oxalate (oxalate of K in a slightly acid stannous solution.)  A small quantity of simple crystals, rhombohedrons or prisms, a large quantity of spots in H or X shapes, with wings like butterfly wings.
  • IRON. One can first isolate the iron particles by using a magnet or electro-magnet. Iron presents itself in different forms.  First, as the product of sharpening, which will be in the form of thin, elongated scales, sometimes with little hooks that are slightly bent. Dust resulting from polishing has approximately the same characteristics.Dust from turning or grinding is composed of more voluminous particles.  Sometimes one sees spiral stripes that are shiny on the more curved surfaces.  On the sides, there are particles that are shorter and thicker, along with pulverized fragments of varying thickness.Debris from a hammer is composed of polygonal platelets, sometimes triangular and often in several layers, which gives the debris a stratified look.  The top layer, the one that has been hit directly, is very dense, shiny, and of a gray-blue color with traces of rust.Residue from the forge includes shorter, flatter fragments in shapes that vary widely. From a clinical and micro-chemical point of view, one characterizes iron with Prussian blue.  One must not operate in the presence of an excess of mineral acids which dissociate the potassium ferrocyanide even in the presence of ferric salts.  Under a microscope, it is quite easy to see the flaky blue precipitate.
  • GRANITE. Light gray dust mixed with black dots.  There are bursts of flat quartz, diaphanous yellowish-green corpuscles with slightly noticeable stripes (feldspar), some small, dark, brown mica chips.
  • SANDSTONE. Fine, heavy, yellowish and regular.  Under the microscope, amorphous, powdery, containing clay (argile), blades of quartz, fat rounded corpuscles (clay schists.)
  • MAGNESIUM. This metal will be characterized by ammonia-magnesium phosphate.  To obtain observable crystals, one must slow down the reaction.  One can do this by placing on the slide a drop of the solution containing the magnesium and adding a drop of ammonia salt; then, next to that, a drop of a solution of phosphate of Na.  Heat this very carefully over a Bunsen burner, then join the two drops together with a drop of ammonia.  If one were looking for ammonia using this same type of reaction, the first drop would contain the solution to be examined plus a very little bit of magnesium chloride; the second drop would contain phosphate of Na added to the bicarbonate of Na; the third drop would be distilled water.One observes orthorhombic prisms with modifications that make them look like roofs; tables shaped like triangles or trapezoids.  Often the prisms have triangular shapes on the inside; these shapes may contain the skeletons of crystals in H or X shapes, with unequal branches like butterfly wings.  These skeletons are almost always found only in slightly concentrated solutions.  Finally, if the concentration is stronger still, there will only be confused aggregates of baton shapes with some groupings in star-shapes or like the plumes of a feather.
  • MERCURY. The metal will be characterized by mercuric chloride (hydrochloric acid in a mercury solution), fine needles dividing rapidly into little specks that turn black in ammonia.
  • PHOSPHORUS. One characterizes this by phospho-molybdate of ammonia.  Most often, yellow globules with a few cubic, octahedric and dodecahedric crystals with rounded angles.
  • PLASTER. Fine mud containing gypsum in various forms.  One can easily change the form of the crystals with hot acetic acid.  When dissolved in hot, concentrated sulfuric acid, it gives an anhydride in the form of rhomboid-shaped prisms with bouquets of needles.
  • LEAD. This metal will be characterized by lead chloride.  With the cooling of the aqueous solution, [one obtains] elongated prisms; often their extremities are hollowed out by irregular cavities or in triangle shapes, with the point directed toward the center.
  • POTASSIUM. One seeks to obtain the formation of chloro-platinate of potassium in the following manner:   Pour a solution of platinum chloride into a solution containing potassium salt.  Slow evaporation allows for the formation of yellow, refringent crystals which are within the cubic system.  In terms of forms, there are cubes, octahedrons and, above all, cubo-octahedrons.  These crystals are sometimes isolated, sometimes in groups of three or four.  The sensitivity of the reaction is quite high.
  • QUARTZ. Fragments that are more or less large and transparent, with various dark layers that can be brown, green or rust colored.  Conchoidal fractures with vitreous tips or spines.  After treatment with hydrochloric acid, it may turn a malachite green color.
  • SLAG/SCORIA. Vitreous structure; often with spherical forms.  No reaction with acids or bases.  Incombustible.
  • SILICA. This is characterized with sodium fluoro-silicate.  One condenses this on a small platinum plate (slightly convex, moistened with water and with the concave part containing cold water.)  The resulting vapors are of fluorated matter supplemented by the material suspected of containing silica—which, if possible, has been melted with carbonate of soda.  The water from the condensation is placed on a holder of varnished Canadian balsam, to which is added a drop of sodium chloride solution.  One observes rosettes and hexagonal tables, bi-pyramidic prisms with star-shaped skeletons and flattened cylinders or ellipsoids.
  • SODIUM. This is characterized by its double acetate of uranyl and sodium.  One operates, using the uranium oxide as a reactive; One concentrates it using heat, but just until the point of dryness [siccation].  One then obtains very clear, regular tetrahedric crystals.  They are light greenish-yellow.  They are seen at the edges of the drops, that is, where there is a maximum of concentration.  This reaction only works definitively with sodium salts, although the other alkaline uranates are insoluble.When there is magnesium in the solution to be analyzed, a triple acetate of uranyl will precipitate along with sodium and magnesium.  This salt presents itself in the form of rhombohedra with modified edges, having the appearance of regular dodecahedrons and icosahedrons, which form when there is very little sodium with respect to the magnesium.  This triple acetate allows for the discovery of minimal quantities of sodium along with large quantities of magnesium.
  • STRONTIUM. One characterizes this with oxalate and with sulfate.  One must have a strong enough concentration of the liquid so that mixing it with the reaction gives a slight clouding effect.  In cold, one obtains crystals that look octahedric but which are, in fact, clino-rhombs.   Other crystals look like little envelopes used to mail letters.  When heated, the octahedrons disappear, and, when cooled, one obtains more or less elongated clino-rhombs.
  • ZINC. One characterizes this metal with sodio-zincic carbonate (an excess of bicarbonate of soda in the solution.)  Tetrahedric crystals refract strongly in light.


Incorporated into mud one may find animal or vegetable debris.  Ruling out the rare case of fossil debris, the determination of which cannot be relied on, one may find organic particles from decomposed plants—ligneous debris, pollen dust, flour, etc.  These elements will be determined through microscopic examination.

In general, it will be advantageous to attach to the report a series of photomicrographs of the preparations.

Here, as an example, is a diagnosis of various flours (Treatise on Criminalistics, Vol. II, p. 866.)

        1. Wheat Flour: Wheat flour takes the form of grains that are more or less large.  The largest are shaped like thick lentils without stratifications.  Viewed straight on, they have no nucleus and only show a few concentric layers.  Seen in profile, they are elliptical, often with a longitudinal groove, and measure 15 to 45 microns.  When treated with chromic acid, they present a central nucleus and a marked concentric striation.  In polarized light, the grains of starch present a black cross, but only as the light is extinguished [crossed polars]. When the flour is old or spoiled, the grains of starch are more or less exfoliated and vulnerable to a 1.75% solution of potassium.
        2. Rye Flour: Rounded grains.  The largest are larger than wheat grains, measuring from 35 – 40 microns, with a maximum of 65.  They are discoid, irregularly bulging or with humps.  The other grains are smaller.  One frequently observes a narrow hilum, generally with three branches; this is characteristic. Unicellular “tector” hairs whose cavity does not enlarge abruptly at the base. Transverse cells with lateral walls that are generally rounded and smooth.
        3. Barley Flour: The grains are smaller, measuring a mean of 25 microns, up to 35 microns.  They are more often elliptical than cylindrical, sometimes in the form of haricot beans.  In polarized light on a black field, one sees a very clear cross, but more blurred than in wheat.  Transverse cells with thin walls and just barely punctuated.  Habitual presence of fine debris from the straw (exterior envelopes formed from the external epidermis of cells having very thick walls, equipped with very short hairs that are elongated in the direction
          of the seed).
        4. Oat Flour: Starch in composite grains that are more or less large, in the shape of ovoid pockets, often pointed or spear-shaped, measuring 15 to 45 microns.  By placing the cover on with a certain pressure, one will spread the mass out into its elements, allowing one to perceive angular, spiny grains of 3 to 7 microns in diameter.  Presence of unicellular “tector” hairs, that are cone-shaped, with thick walls and often joined together.
        5. Corn Flour: In the enveloping tissue, one sees grains that are squeezed one against the other and agglutinated.  In contrast, in the corn flour, the grains are free.  The former have sharp points, are polyhedral, often having a neck, and are never stratified.  One will note a central dent in the form of a cross or star.  In the latter, the cells are more rounded and isolated.  The size is from 15 to 30 microns.
        6. Rice Flour: The grains have sharp points, resembling crystals.  Certain grains are elongated into points, and are rarely assembled in regular ovoid masses.  The simple grains are 3 to 8 microns in diameter; complex ones are 20 – 40 microns.  There are also hulls that are more or less voluminous and more or less difficult to disaggregate.  One should not find tector hairs.  The tubular cells, when they exist, are always small, and the transverse cells are never punctuated.
        7. Buckwheat Flour: This flour presents itself in small grains, usually polyhedral, from 3 – 15 microns in diameter;  free or joined in a mass.  In the largest grains, one sees a central hilum, dividing into two or three sections or rays.  The hulls are irregular, fairly refringent and composed of simple grains or compact masses of a grayish color.  The long, sinuous, colored cells representing the external envelope are characteristic.
        8. Millet Flour: Is presented in the form of polyhedral grains, with a noticeable hilum. Certain grains reach 10 microns in diameter.
        9. Haricot Bean Flour: Sclerotic cells in rows, whose form varies according to the viewer’s perspective — in transverse sections, straight on, or whether the upper or lower surface.  Polygonal cells, called hourglass cells, with a prismatic channel that does not exist in other legumes. The cotyledon cells, either whole or broken, are distinguished by their thickness and the very clear punctuation of the cell walls, often separated by lacunae that are more or less large.  Ovoid or reniform grains of starch, 35 microns long by 24 microns wide, with concentric striations and a “sprung” [sic] hilum.
        10. Pea Flour: Greenish yellow; no crystals in the hourglass cells; cells constituting the parenchyma of the tegument, or covering, are very large; cells of the envelope of the cotyledons are very irregular; grains of starch are reniform and distinctly curved, without concentric layers; with a linear hilum that is either straight or undulating; the grains measure 35 – 50 microns.
        11. Lentil Flour: Cells in rows, shorter that those of peas and with a cavity that contains brown colorant matter.  Hourglass cells without crystals, smaller and more regular than those of peas, parenchyma cells with a semenaderm that is not separated by large lacunae as in the case of peas or haricot beans.  Cotyledon cells in a uniform direction.  Ovoid starch, rarely surpassing 30 microns long by 10 microns wide—but able to attain 40 X 25—with a linear hilum that is sometimes fissured, but often extending the entire length of the grain and with concentric striations less visible than those of the haricot bean.
        12. Feverole [Tr. a smaller variety of fava bean] Flour: Grains of starch, either free or enclosed in the cells of the cotyledon; oval, elliptical or reniform. A fissured hilum along the length or transversally, which is often branched in various ways.  The debris of the tissue of the cotyledons is formed of polygonal cells with very thick walls; the lacunae in the angles are easily visible.  Other debris formed of smaller polygonal cells with thinner walls (fragments of embryos.)  In glycerinated water, the cotyledon cell walls take on a blackish tint because of the air trapped in the interstices.
        13. Broad Bean (Fava Bean) Flour: The grains are more irregular than those of the feverole bean; there are fissures along the edges.
        14. Potato Starch: Grains are 50 – 60 microns long and 30 – 60 microns wide.  They are disposed around an eccentric hilum, most often situated on the narrowest extremity from which the striations rediate.  The starch is insoluble in cold water, alcohol and ether.  Heated to 80 degrees in water, the envelopes break open, leaving an opalescent mass, which is the starch.  When mixed cold with a few drops of an iodine solution, a blue color appears which will disappear at 100 degrees and reappear upon cooling.  In polarized light, one obtains dark crosses at the maximum brightness and when the light is extinguished.
        15. Sago Starch: Grains of irregular size, most often elliptical, round or oval, sometimes with bumps along the contours.  Certain grains are composed of one central grain to which are attached two or three smaller granules.  The large grains measure 50 – 65 microns in length; the small ones are scarcely more than 10 – 20 microns.  On most of the large grains, there is a very clearly apparent hilum that is eccentric, represented by a transversal or oblique fissure that may be simple or star-shaped.  Debris of the medullary parenchyma, sclerenchymatous cells.
        16. Manioc Starch (Tapioca): When the starch has not been washed and dried, it consists of a fine powder that is dirty white, dull and in grains that are rarely grouped; the grains are rounded on one side and, on the other side, present a surface that is flat or in polyhedrons of three or four faces. When viewed flat, the grains appear globular and present a very clear hilum often elongated toward the flattened side. The concentric layers are not always visible. The large grains are 25 – 30 microns in diameter; small ones are 5 – 15 microns. When the starch has been heated, as is usually the case with tapioca, it presents itself as an agglomerated mass, which is white, very hard, elastic and composed of irregular grains.  These granules are very hard to thin out in cold water.


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