40 ANALYSIS AND ADULTEEATIONS OF BUTTER. 



It would be of considerable interest to know the propor- 

 tions of stearin, palmitin, and olein contained in butter and 

 other fats, but there are no methods of separating these 

 substances or the acids they yield with anything like quanti- 

 tative precision. Moreover, if it were really possible to 

 separate them the results would be only of secondary 

 importance, and in no way superior to the indications 

 afforded by the melting point, for mixtures of fats of high 

 melting point and of liquid oils could easily be made con- 

 taining stearin, palmitin, and olein in the same proportion as 

 these glycerides occur in butter. Tests founded upon such 

 proportions would be quite as fallacious as the specific gravity 

 of milk, if used alone, and not as a corroboration to the 

 results obtained by some more trustworthy method. It 

 should here be remarked that it is by no means certain 

 whether butter-fat really does contain either stearin or the 

 ordinary normal olein. Stearin seems to be entirely absent, 

 and the liquid glyceride present may well be a butyrolein, 

 such as given by Bromeis. Dr. Tidy, in a paper read before 

 the Society of Medical Officers of Health, denied that butter 

 contained more than traces of palmitin, stearin, or olein. 

 But Dr. Tidy does not state what butter, in his opinion, 

 consists of, or upon what grounds his statement is based. 

 Certain it is, that if there is any stearin its quantity must be 

 infinitesimally small, as the fatty acids, either when crys- 

 tallized from alcohol or precipitated fractionally by acetate of 

 magnesia, do not yield crystals of the composition of stearic 

 acid or a precipitate of stearate of magnesia. But by the 

 former of these methods a beautiful white acid, crystallising 

 in tufts of silky needles, agreeing in physical properties, 

 solubility, etc., with palmitic acid, may be obtained, and 

 this acid seems to constitute a large proportion of the 

 insoluble fatty acids of butter-fat. . 



The magnesium salt of this acid was found to contain 



