ESTIMATION OF FAT — INDIRECT. 



12S 



Faber has, however, shown that very accurate results may be 

 obtained by measuring the volume of cream thrown up from 

 skim milk, after whirling in the lactocrite for one hour, and 

 dividing by 3. 



It has been proposed to deduce the percentage of fat in milk 

 from the opacity of the sample. Various forms of " lactoscope " 

 have been proposed which measure either the thickness of the 

 layer of milk which obscures a given light, or the amount of 

 light passing through a given layer of milk. 



The accuracy of the lactoscope is approximate only, and the 

 instrument has already been described. 



The calculation of the fat from the specific gravity and total 

 solids has already been described. 



The author has tried an expansion method, which depends 

 on the difference of the expansion by heat of fat and milk serum 

 — that of the former being about three times that of the latter. 



Densim.etric Method of Fat Estimation. — By placing 

 about 200 c.c. on a pleated filter and collecting such portions as 

 run through in the first quarter of an hour, the milk serum — i.e., a 

 solution of the solids not fat in water — may be separated without 

 much change in composition. A series of experiments by the 

 author showed that the solids not fat in the filtered milk were, 

 after correcting for the volume of the fat removed, on the av(>raL,'e 

 O'Vl per cent, lower than in the unfiltered milk. 



Vieth gives the following expeiiiuent : — 200 c.c. of milk were 

 filtered; after one hour 5() c.c. of milk had run through; after 

 four and a half hours more, 26 c.c. were collected ; and ln8 c.c. 

 were poured out from the filter. 



The results of analyses of these four milks were — 



Tiital solids, 

 Fat, . 



Siiliils not fat, 

 I'rcitein, 



Original j First 



Milk. 



Per cent. 



13-42 



4-43 



S-99 



Filtrate. 



Per cent. 

 9U 

 06 



y -1 IS 

 36S 



Secniiil I L'ft on 

 Filtrate. Filter. 



Pert-tnt. ! Ptr cent. 



S 14 : 13-9,"i 



I >•():! '. 4 -SI) 

 s 11 9-l.> 



•2 4:? 3 S9 



For eve'-y 100 parts of water there were present 



Soliils not fat, 

 Prcitiin, . 



10-38 



4 123 



9-99 



4-0o 



8 -83 

 2 -Go 



10-63 

 4-52 



The differences as compared with the original milk were 



Siilids not flit, 

 Protein, 



-0-39 

 -0-18 



l-5.> ' +0-25 

 •1-.5S j +0-29 



