96 MILK PRODUCTS 
watery solution with fuller’s earth and filter- 
ing. The filtrate is notably paler if caramel is 
present. Fuller’s earth differs in efficiency, and 
each sample should be tested on known solutions. 
Preservatives.—The preservatives used in milk 
may be found in limited amount in butter, but a 
mixture of boric acid and borax is often added as 
a substitute for salt. 
Glucose is sometimes used as a preservative, 
especially in butter intended for export to tropical 
countries. Crampton found as much as 10% 
in a sample of highly colored butter intended 
for exportation to Guadeloupe. For the de- 
tection of glucose the phenylhydrazin test might 
be used. For determination Crampton used the 
following method: 10 grams of the sample were 
washed with successive portions of convenient 
bulk, the solution made up to 250 c.c., and an 
aliquot portion determined, as given for lactose 
on page 32. The solution may also be clarified 
by alumina-cream or acid mercuric nitrate and 
examined in the polarimeter. 
Boric Acid.—25 grams of the sample are melted, 
the watery portion separated and tested as de- 
scribed on page 62. 
