ANALYSIS OF BUTTER-FAT. 41 



4 '43 per cent, of magnesium, wLilst the formula of pabnitate 

 of magnesium requires 4'49 per cent., and of the stearate 

 4' 06 per cent. 



As many years had passed siace Bromeis published the 

 results of the analysis of hutter, and as, moreover, as we 

 have seen, several inaccuracies had heen pointed out in his 

 figures, we thought it worth while, in 1874, when the neces- 

 sity for a method was more than usually felt hy analysts, to 

 re-investigate that part of the subject which deals with those 

 constituents which, are characteristic of hutter, namely, the 

 several volatile fatty acids enumerated ahove, and which, as 

 we have not attempted their separation from each other, we 

 will, for convenience sake, include in the present chapter 

 under the name of hutyrie acid, as this is doubtless the by 

 far predominant representative of the group. We do not, 

 however, wish to convey the impression that butyric acid 

 alone is present. 



As the first, and perhaps the most important result of our 

 investigations, we found, that the amount of butyric acid in 

 iutter-fat is very much larger than was formerly believed, 

 about foxu' times as great as stated by Bromeis. 



As the second, pre-eminently practical result, it became 

 clear, that the amount of butyric acid in butter-fat is very 

 constant, and nearly independent from the breed of the cow 

 which forms the butter, from the food, the season, the mode 

 of preparation of the butter, and from other conditions, 

 which might have been supposed to exert an influence upon 

 the composition of the fat. 



^KTumerous experiments and determinations have convinced 

 us of the truth of these important facts, and hundreds of 

 analyses, made both by us and the large number of other 

 chemists, who have, since 1874, repeated our experiments, 

 prove their correctness. 



It wiU, we trust, be found interesting to give a sketch of 



