REPORT OF THE CHEMIST. 



Sir: I have the honor to submit the following summary of the 

 work done in the Division of Chemistry during the year 1886. 



DAIRY PRODUCTS. 



A careful study has been made of the best methods of determining 

 the foreign fats wliich are used in the adulteration of butter. 



The expressions "fats" and "oils" designate those natural products 

 of animals and vegetables known as glycerides. Chemically consid- 

 ered they are the normal propenyl ethers of the fatty acids, or, in 

 other words, compounds of the triad alcohol, glycerine, with the fatty 

 acids. The term "fat" is applied to such bodies when they aref solid 

 at ordinary temperatures, and ' ' oil " when they are semi-solid or liquid. 

 Those which are most important are: 



Tri-stearin, C3H5(Ci3H3502)3, occurin^ in natural fats. It may be ob- 

 tained in a considerable degree of purity by repeated crystallizations 

 from ether. It crystallizes in plates of a pearly luster. Its melting 

 point is 55° C. 



Tri-palmitin, C3H5(Ci6H3i02)3, is found in animal fats and palm-oil. 

 It crystallizes with a pearly luster from ether. The crystals have a 

 melting point of from 50° to 66° C. 



Tri-butyrin, C3H5(C4H702)3, occurs chiefly in butter. At ordinary 

 temperature it is liquid, and has a distinct and peculiar odor and 

 taste. 



Tri-olein, C3H5(Ci8H3302)3, occurs in animal fats and in almond and 

 olive oil. At ordinary temperatures it is liquid, neutral to test pa- 

 pers, and has neither taste nor smell. 



Minute quantities of tri-myristin, tri-caprin, and tri-caprylin are 

 also found in butter. 



Pure butter fat is supposed to contain : 



Per cent. 



Of tri-olein, about 42. 5 



Of tri-stearin, about 51. 



Of tri-butyi-in, about 6. 3 



Of other glycerides, about 2 



100.00 



Olive oil is composed chiefly of tri-palmitin and olein. Tri-stearin 

 is the chief constituent of mutton fat, it having only small quantities 

 of olein and palmitin. Beef fat has somewhat more palmitin and 

 stearin than mutton tallow. Lard has more olein. It is thus seen 

 that in dealing with butter fats and their substitutes we have to con- 

 sider chiefly tri-olein and stearin, and, in smaller quantities, tri-pal- 

 mitin, butyrin, &c. It follows, therefore, that the chief differences 

 in the general characters of these substances will be due to the dif- 

 ferent proportions in which these glycerides are mixed and to such 

 other physical differences as the various sources of the substances 



(277) 



