104 



(3) Adams method. Examination of Schleicher and ScMill's "fat-free'^ 

 paper showed that the strips contained a little over 1 mg-. each of 

 material soluble in ether, and that 2 hours were sufficient for extrac- 

 tion of this material. In usinj^ tliis mctliod the milk was poured upon 

 the strip, the strip dried for about halt an hour, and then extracted in a 

 Soxhlet apparatus. With regard to the duration of this latter extraction, 

 experiments showed 3 hours to suflice for whole milk, but in his com- 

 parisons of the Adams metliod with others the author extracted tVu- 5 

 hours in case of whole milk and for 12 hours in case of skim milk. The 

 parallel tests by the Adams method agreed more closely than those by 

 any of the other methods tested. 



The averages of parallel results (tbtained in comparisons of the differ- 

 ent methods on the same samjiles of milk are given as follows: 



Percentage of fat in milk by different methods. 



Single cow's milk < 



Mixed milk \ 



Single cow's milk 



Two parts of skim milk and one of whole. 



Mixr.lmilk '-'4 hours nl.l 



Mixfd milk 48 hours old 



Ccntrifngal skim milk 



Gravimetric methods. 



Pumico 

 stone. 



Percent. 

 3.65 

 3.64 



2.95' 



Powdprcdl 

 earthen- Adams, 

 ware 



Per 



cent. 

 3.66 

 3.63 

 3.09 

 3.08 

 2.67 

 2.55 

 2.38 

 2.19 

 1.35 

 0.85 

 0.76 



I Lacto- 

 I crite. 



Percent. 

 3.74 

 3.73 

 3.18 



2.76 

 2.60 

 2.49 

 2.28 

 1.43 

 0.94 

 0.86 

 0.74 

 0.48 

 0.40 

 0.33 



Per cent. 

 3.71 

 3.62 

 3.13 

 3.10 

 2.72 

 2.52 

 2.43 

 2.23 

 1.41 

 0.90 

 0.80 

 0.69 

 0.42 



0.28 



Soxhlet's 

 aeromct- 



ric 

 method. 



Percent. 



3.71 

 3. t> 

 3.2- 



2.77 

 2. .'■>« 

 2.49 

 2.:n 

 1.47 

 1.02 

 1.94 



* Not powdered after drying. 



The differences between the results by the Adams method, the earth- 

 enware method, and the lactocrite are expressed in the following state- 

 ment : 



Differoiices bctwooii — 



Ailanis and i'arth«niwaro 



Adiuiis and lai-tocritc 



Lactocrite and earthenware 



Maximum. 



-fO.U 

 -fO.ll 

 -1-0.06 



Minimum. 



-fO.05 

 -f0.02 

 -0.03 



ATorage. 



+0.088 

 +0. 0.">2 

 -1-0. 03."> 



The author feels certain that the invariably higher results by t lie 

 Adams than by the earthenware method can not J)e attributed to tlie 

 l>i'esence of an unaccounted for ether extract in the pa])er. and is 

 inclined to the view that owing to the tineness of the interstices of the 

 paper the fat globules are notable to i)enetrate the paper and so remain 

 on the surface, largely freed from milk serum, where they arc more 

 advantageously exi)osed to the solvent action of the ether. 



