DAIRY PRODUCTS. 91 



ing is accomplished. I have been able to put 5cc. of milk on a strip of 

 paper, hang it over a sand bath and have it rolled and in the extractor 

 within five minutes. 



I mention this to show that even in the matter of gravimetric deter- 

 minations by whicn the areornetric method is finally judged, there is 

 still a certain limit of variability. 



I will return now to the subject more immediately under discussion. 

 Schmoeger further says 1 that with skimmed milk, buttermilk, and such 

 milks as have stood twenty-four hours on ice the ether-fat solution sep- 

 arates difficultly or not at all. To avoid this lie recommends, after the 

 addition of the potash, fully five minutes shaking, in order to form but- 

 ter of the fat. Then the ether is added and the process continued as 

 usual. In this case the percentage obtained by the areometric method 

 must be increased .1 per cent, in order to agree with the gravimetric de- 

 terminations. Schmoeger further recommends that skimmed milk or 

 sweet buttermilk after treatment with potash be shaken with 10 grams 

 potassium sulphate until the latter is dissolved. But this method also 

 influences the specific gravity of the ether-fat solution, and the correc- 

 tions to be made are found in the table given. 2 



Soxhlet himself 3 has called attention to the fact that with skimmed 

 milk the ether-fat solution does not readily separate. A special scale 

 has been constructed for such fat-poor milks giving areometric readings 

 from 21.1 to 43, with the corresponding percentages of fat. For such 

 milks Soxhlet proposes the following treatment, viz : A soap solution is 

 made by taking 15 grams of a steariue candle, adding to it 25cc. alco- 

 hol, and lOcc. of the potash solution of the strength before given. The 

 stearine is saponified by heating the mixture, and after the solution has 

 become clear it is made up to lOOcc. with water. From .4 to .5cc. of 

 this solution is added to the milk under examination, and after a good 

 shaking the rest of the process is carried on in the usual way. After 

 the first thorough shaking on the addition of the ether the light jolting 

 must be continued for fifteen minutes at intervals of half a minute in 

 order to have the ether solution collect at the top. At longest, the so- 

 lution separated after three or four hours. 



Halenke and Moslinger 4 call attention to the fact that if samples of 

 milk are kept for some time, even on ice, the ether-fat solution will no 

 longer separate. They prefer in such cases a modification of Lieber- 

 mann's method, which they describe. In general I may say the areo- 

 metric method has met with the approval of all analysts who have used 

 it with exception of Preusse 5 , but Soxhlet 6 has shown that Preusse did 

 not understand how to use the apparatus. 



1 Op. cit. 

 *Ibid., p. 132. 



3 Zeit. landw. Vcr. Bayeni, 1882, p. 18. 

 4 Ver. Bay. Vertreter d Angewand. Chem., p. 110. 

 5 Mittheil. Reichsgesundheitsamt, vol. I, p. 378, 

 it. landw. Ver. Bayern, 1881, p. 700. 



