paper in this solution for a few minutes, then remove and dry it. If boric acid either free or combined is present, the turmeric paper will be turned to a cherry-red color.

Another way of making this test.—U. S. Dep. of Agr., Div. of Chem., Bul. 65, p. 110: Make strongly alkaline with lime water, 25 grams of the milk, and evaporate to dryness on the water bath. Destroy the organic matter by igniting the residue. Dilute with 15 cc. of water and acidify with hydrochloric acid. Then add 1 cc. of the concentrated acid. Dip a piece of delicate turmeric paper in the solution; and if borax or boric acid is present, it will have a characteristic red color when dry. Ammonia changes it to a dark blue green, but the acid will restore the color.

(Turmeric paper may be prepared by dipping pieces of smooth, thin filter paper in a solution of powdered turmeric in alcohol.)

Salicylic Acid

(This is not often used as a preservative of milk.)

Leach suggests the following method for its detection.—Dissolve one gram of mercury in 2 grams of nitric acid (sp. gr. 1.42) and then add to the solution the same volume of water. Add 1 cc. of this reagent to 50 cc. of the milk to be tested, and shake and filter. The perfectly clear filtrate is shaken with ether and the ether extract evaporated to dryness. Then add a drop of ferric chlorid solution, and a violet color will be produced if salicylic acid is present.

BUTTER

Butter is often colored with annatto, saffron, turmeric, marigold or coal-tar colors. By a certain process, stale or old butter is sometimes worked over and made to appear fresh for a time. This is sold under the name of “process” or “renovated” butter. Foreign fats like cottonseed oil, sesame oil, or oleomargarine may be substituted for or added to pure butter.

COLORING MATTER

Martin’s Test.—Add 2 parts of carbon bisulfid, a little at a time and with frequent shaking, to 15 parts of alcohol. Shake 25 cc. of this solution with 5 grams of the butter, and let stand for some time. The carbon bisulfid dissolves out the fatty matter and settles to the bottom. The alcohol remains on top and will dissolve out any artificial colors that may be present. If only a little coloring matter is present use more of the butter.

Annatto

Evaporate a portion of the extract to dryness and add sulfuric acid to the residue. If annatto is present a greenish-blue color forms. Should a pink tint result the presence of a coal-tar color is to be suspected.

Coal-Tar Colors

These colors will dye wool or silk if pieces of the fiber are boiled in the diluted alcoholic extract, which has first been acidified with hydrochloric acid. The normal butter coloring matter will not dissolve when thus treated.

Geisler’s Method.—To a few drops of the clarified fat on a porcelain surface, add a very little fullers’ earth. If a pink to violet-red coloration is produced in a short time the presence of an azo-color is indicated.

Saffron

When saffron is present, nitric acid colors the alcoholic extract green, and hydrochloric acid colors it red.

Turmeric

Add ammonia to the alcoholic extract, and if it turns brown it indicates the presence of turmeric.

Marigold

Add silver nitrate to the extract, and if it turns black the presence of marigold is indicated.

Process or Renovated Butter

Heat a little of the suspected butter in a spoon or dish, and if it is process butter it will sputter, but not foam much. Make the test also with some butter known to be pure and fresh.

Hess and Doolittle Test.—Melt some of the butter (say 40 grams) at about 50° C. If the butter is pure and fresh the melted fat will clear up almost as soon as it is melted, while the fat of process butter remains turbid for quite a while. After most of the curd has settled, decant as much as possible of the fat. Pour the remainder on a wet filter. Add a few drops of acetic acid to the water that runs through from the filter, and boil. If it was ordinary butter this filtrate will become milky, but if process butter a flocculent precipitate will form.

Oleomargarine

Immerse a test tube, containing some of the filtered fat, in boiling water for 2 minutes. Make a mixture of 1 part glacial acetic acid, 6 parts ether, and 4 parts alcohol. Add to 20 cc. of this mixture in a 50 cc. test tube, 1 cc. of the heated fat which may be transferred by means of a hot pipette. Stopper the tube and shake it well. Immerse in water at 15° or 16° C. Pure butter when thus treated remains clear for quite a while. There will be only a very little deposit after standing an hour, but oleomargarine gives a deposit almost immediately, and in a few minutes there will be a copious precipitate.

When the oleomargarine in butter is in about the proportion of 1 : 10, it will not separate much short of 15 minutes.

Cottonseed Oil

The presence of this oil may be detected by Halpen’s test, which is given under lard, page 60.

CHAPTER II
MEATS AND EGGS

Meats are preserved by treating them with potassium nitrate, boric acid, sulfurous acid, salicylic acid, or benzoic acid. Cheap meat may be substituted for the more expensive. A few cases of horse meat in mince meat and sausages have been discovered. Diseased and stale meats have been found on the market. Canned meats often contain zinc, tin, and lead, and sometimes even arsenic. Aniline-red or cochineal-carmine may be added to improve the color of chopped or ground meats. Starch is sometimes added to sausage and similar meat. Fish and oysters may be preserved with boric acid or borax.

FRESH AND SMOKED PRODUCTS—PRESERVATIVES

Potassium Nitrate (Saltpeter)

Corned and smoked meats are usually preserved with saltpeter. Since smoked and cured meats are used in making potted meats, saltpeter is quite frequently found in the latter. It may be detected by the usual test for nitrates since no other nitrate is apt to be present, though one may identify the metal by the qualitative test for potassium.

To test for nitrates treat a little of the meat with 2 or 3 cc. of a 1 per cent solution of diphenylamine in strong sulfuric acid. If a nitrate is present a deep blue color forms instantly, which is not obscured by the charring effect of the acid.

Boric Acid

Pick apart into fine pieces about 25 or 50 grams of the lean meat and warm with a little water which has a few drops of hydrochloric acid in it. Soak a piece of turmeric paper in the extract, and if boric acid is present the paper will be colored rose-red when it is dry. A weak alkali turns this colored paper olive.

Another method is to burn a piece of the meat to an ash, after being treated with lime water. Make a solution of the ash and make slightly acid with hydrochloric acid. Then test with the turmeric paper with the same results as in the above method.

Sulfurous Acid

U. S. Dep. Agr., Bureau Chem., Bul. 13, Part 10: Digest 40 or 50 grams of the meat