DAIRY PRODUCTS MILK AND CREAM. 35 



21. TOCHER" TEST FOR SESAME OIL. 



Dissolve 1 gram pyrogallol in 15 cc of concentrated hydrochloric acid. Mix this 

 solution with 15 oc of oil in a separatory funnel and allow to stand for a minute. 

 Draw off the aqueous layer and boil for five minutes. In the presence of sesame oil 

 it becomes colored red by transmitted light and blue by reflected light. 



22. MICROSCOPICAL EXAMINATION. b 



Dissolve in a test tube from 2 to 5 grams of oil or fat in about 10 cc of ether, plug 

 the test tube lightly with cotton and allow to stand 15 or more hours in a moderately 

 cool place. 



The most characteristic crystals are obtained when the crystallization proceeds 

 slowly and at temperature of from 22 to 24 C. The first crop of crystals may be 

 examined and the mother liquor separated and set aside for further crystallization. 



In order to get rid of the oleins, Gladding has suggested the following: 



Dissolve in an Erlenmeyer flask 5 grams of melted fat in 10 cc of absolute alcohol 

 and 5 cc of ether, stopper with cotton and place in ice water for about one-half hour, 

 until the more crystallizable portions of the fat have separated. The crystalline part 

 is separated by filtration through a filter paper moistened with alcohol, and washed 

 with the alcohol-ether mixture. After drying in the air for some time the crystals 

 are dissolved from the paper by means of ether and then treated in the same way as 

 described in the first method. When the crystals are ready to examine a drop is 

 removed with a pipette, placed on a slide, a drop of cotton oil or olive oil added, and 

 a cover slip pressed gently down. 



III. DAIRY PRODUCTS. 



By J. A. LECLERC, 



State Experiment Station, Geneva, N. Y. 



(A) MILK AND CHE AM. 

 1. GENERAL DISCUSSION. 



There are three kinds of adulteration generally practiced with milk. First, 

 addition of water, which is the simplest and the most common practice. Second, 

 removal of fat or the removal of fat and addition of water. This double adultera- 

 tion is used in order not to disturb the specific gravity. Third, the addition of 

 preservatives, most commonly formaldehyde, boric acid, or borax. 



The determinations ordinarily made in the examination of milk and cream are 

 specific gravity, fat, total solids, solids not fat, and the detection of preservatives and 

 coloring matter. The specific gravity alone is of little value in judging the purity of 

 milk, owing to the fact that the increase of specific gravity produced by the removal 

 of cream may be reduced by the addition of water. One of the most important con- 

 siderations is the relation of the solids not fat to the fat. In milk it has been found 

 that this ratio does not vary w r idely from 9:4. 



2. DETERMINATION OF TOTAL SOLIDS. (1 



Heat at 100 C. to constant weight about 3 grams of milk in a tared platinum, 

 aluminum, or tin dish' of 5 cm diameter, with or without the addition of 15 to 30 

 grains of sand. Cool and weigh. 



Phnrr.i. .Tourn. mid Trans., 1891, 639. Chem. Zeit,, Rep., 1891, 5, 15-33. Bcncdikt and Lewko- 



\vitsrh, Oils, Fats, mid Wnx.-s. p. :tl'.. Wintmi. <onn. Kxpt. Sta. Kept.. I'.HM). pt. 2. p. 153. 



M'.S. Dept.of AKI-., Div.of Clicin., Kul. l:;, pt. -I. p. 111). Gladding, Jour. Am. Chem. Sot 1 ., 18%, IS. is-.t. 

 \Vilry I 'rin.it Prac. A^ri. Anal., vol.:;, pp. :;i:>, :;n;. Win ton, Report Conn. Expt. Sta., 1900, pt. 2, p. M.\ 



"Jour. Am. ('hem. Soe., IS ( .M>, IS, l,xi. 



11 T. S. I)ept. of Atfr., Div. of ('hem.. Hill. Hi revised, p. 54. 

 Appendix, p. ! .1. 



