REPORT OF THE MICROSCOPIST. 99 



SO liquid -n-hen cold that its crystals will swim incrusted on the surface 

 of the oil. When a little of this floating incrustation is bruised gentlj^ 

 in oil and mounted, beautiful discoid cr3\stals will appear under the mi- 

 croscope. When normal crystals of fat of any description are mounted 

 in oil it is difficult to preserve specimens of them for a long period, 

 owing to their tendency to dissolve, especially at temperatures exceeding 



CHEMICAL TESTS FOR BUTTER, OLEOMARGARINE, AND BUTTERINE. 



Oleomargarine made under the French patent, consisting mostly of 

 beef fat, is easily detected by pouring a few drops of concentrated sul- 

 phuric acid on a portion about the size of a bean and mixing quickly 

 with a glass rod. The mass at once assumes a light amber tint, soon 

 turning darker and richer in color. After a period of from fifteen to 

 thirty minutes it turns to a well-defined crimson scarlet. After a lapse 

 of twenty-four hours it becomes the color of dark walnut. 



Within the last six months I have failed to find any of this grade of 

 butter substitute in Washington markets. It is giving way to various 

 cheaper compounds, known as butterine. 



True oleomargarine may be detected also by boiling a sample of it in 

 an iron spoon, when the odor of burnt fat is given off. Butterine can- 

 not be tested by this process satisfactorily, owing to the presence of 

 butter in the mixture, the butyric acid of the butter being the most 

 prominent odor observed. 



If samples of pure butter, oleomargarine, and butterine are exposed to 

 a temperature of 75° F,, for a period of one hour, the last named will 

 become slightly glossy, and at 85° will become almost semi-fluid, while 

 the other two samples named will not appear to the naked eye to be 

 thus aflected and will preserve their sharp angles. 



When oleomargarine or butterine is newly made, crystals of fat are 

 seldom observed in it when viewed under the microscope; but in course 

 of time, owing to their being subjected to bght and increased rise of 

 temperature in the stores, both exhibit crystals of fat more or less. In 

 the butter substitutes of commerce, the crystals are seldom absent, but 

 dark, nitrogenous, yellow, translucent bodies are always seen in them 

 and are characteristic of them. These latter substances are never found 

 in pure butter. When butter substitutes are sold as butter, they ex- 

 hibit only the faint odor and taste of butter, and one is puzzled to know 

 whether the article is genuine or not. In such cases it will generally be 

 found to be cither oleomargarine or butterine. When the suspected 

 substance has a bad odor, and tastes like butter, it is probably old but- 

 ter, provided it exhibits no dark yellow bodies when viewed under a , 

 power varying from 75 to 250 diameters. j 



now TO DETECT THE CRYSTALS OF LARD BY THE NAICED EYE. 



Procure a piece of glass ; ijlace a small portion of the lard on it, cov- 

 ering it with a Ihick microscopic glass disk j press the parts together so 

 as to form a thin film of the lard between, as described in the case of 

 butter. View the glass and lard thus secured before a strong light, 

 when white specks will be observed in the lard. The transparent por- 

 tion represents the oil, the wliite specks the crystals of fat. In this 

 way fats may frequently be detected in oleomargarine and butterine. 

 Pure butter treated in this way exhibits a plain, even color. Mixed 

 butters have a streaky appearance, owing to their different densities 

 and colors. 



