PRESERVATIVES AND DIRT 197 
an irritant effect upon the kidneys. Its presence in milk 
is easily detected by the following test: 
_Add 2 to 3 drops of sulphuric acid and about the same 
amount of ether to 20 c.c. of milk, then shake the mix- 
ture; evaporate the ether solution and treat the residue 
with 40 per cent solution of alcohol, and filter. The 
Fig 60.—Sediment Tester. 
addition of a few drops of ferric chloride to the filtrate 
will produce a violet color in the presence of salicylic 
acid. 
DIRT IN MILK. 
There is undoubtedly more dirt consumed through 
milk than through all other food products combined. 
