242 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
formula gives the most accurate results when compared 
with gravimetric determinations. This formula is as 
follows: 
100 S—Sf 
Per cent. solids not fat= (wore = 
1) x (100 —f) 2.5 
S=specific gravity; f=per cent. of fat. 
The results obtained with this formula will not differ 
more than 0.25 to 0.5 per cent. from those obtained by 
the gravimetric method. A table prepared by Shaw and 
Eckles, which renders it unnecessary to make the cal- 
culation for each sample, will be found on pages 243 to 
245. The Babcock formula determines the per cent. of 
solids not fat, but this table gives the per cent. of total 
solids; it is a modification of one prepared by Dr. Bab- 
cock. In the table the per cent. of total solids in any 
given sample will be found at the intersection of the 
column headed by the number representing the Jactom- 
eter reading (Quevenne degrees) and the line corre- 
sponding to the fat per cent., provided the lactometer 
reading is a whole number. If the lactometer reading is 
not a whole number then the per cent. of total solids is 
found for the whole number and to this is added the 
fraction found opposite the decimal in the table for 
“proportional parts.” Take, for example, a sample of 
milk with a lactometer reading of 33.5 and a fat per 
cent. of 3.5. At the point where the column headed 33 
and the line marked 3.5 per cent. fat intersect are the 
figures 12.46. In the table for “ proportional parts,” 
opposite the decimal .5 is the fraction .13. This added 
to 12.46 equals 12.59, which represents the per cent. of 
total solids. 
