EEFOKT OF THE CIIEMIST. C5 

 SATURATION EQUIVALENT. 



(5) The quantity of alkali required to saponify the fat is another 

 means of judging of the purity of a butter. 



Batter fat contains an acid (butyric) which has a lower molecular 

 weight than the oleic, margaric, andpalmic acids, which form nearly all 

 of tim common butter adulterants. By reason of this difference the quan- 

 tities of alkali necessary for saponification are different for equal weights 

 of butter fats and those of lard, tallow, &c. This difference is strikingly 

 illustrated in the table of analyses, and is the most reliable evidence of 

 the purity or impurity of the sample under consideration. The manip- 

 ulation of the analysis being an easy one, the determinations of the sat- 

 uration equivalent is generally the first test in determining the genuine- 

 ness of the butter. If this number should fall under 250 it would be 

 safe to call the sample genuine butter. 



SOLUBLE ACIDS. 



(6) Pure butters have a large percentage of acids soluble in water. 

 The percentage of these acids to the total weight of direct butter fat is 

 about five. In the analyses given this percentage does not fall below 

 4.49, nor rise above G, except in one case of Jersey butter, made under 

 exceptional conditions. In the butter substitutes these acids rarely go 

 above .5 per cent. Their determination, therefore, is an almost certain 

 one of the purity of the sample. 



OPTICAL PROPERTIES. 



(7) Pure unmelted butter, when reviewed through a selenite plate by 

 polarized light, presents a uniform tint over the whole field of vision. 



On the other hand, butter substitutes give a field of vision of a mot- 

 tled appearance. This phenomena is so marked that, with a little ex- 

 perience, the observer will be able to tell a genuine from an artificial 

 butter with a fair degree of accuracy. While the examination should 

 never stop with this optical test above, it can be advantageously used 

 as a preliminary step. 



MILK ANALYSIS. 



Under instructions from this Bureau, Mr. Woodbury Blair placed two 

 cows of his herd, Belle and Kitty, under special control. The object 

 of the experiments was not to determine the total quantity of milk pro- 

 duced nor of the rations consumed, but to see if the character of the 

 milk was influenced by the admixture of ensilage with the food. The 

 cows were first placed on a diet of ensilage, bran, &c, cotton-seed meal. 

 The milk of the cows taken in the morning was subjected to analyses 

 for ten consecutive days. 



The food was then changed to chopped hay, bran, and corn-meal, and 

 the analyses made as above. The rations were then changed to those of 

 the first trial, and the analyses continued for two weeks longer. At the 

 time of each change of diet the constituents of the milk were subject to 

 some variations, which passed away after a day or two. In general it 

 may be said that the use of ensilage produced no marked change in the 

 character of the milk. In the case of Belie the percentage of sugar 

 5 A— '84 



