385 
that in the examination of a foodstuff for artificial colors the chemist 
ofttimes encounters the difficulty of distinguishing a harmless from 
a poisonous color. As a rule it is an easy matter to determine when 
a synthetic color is present, but very difficult ofttimes to determine 
its precise nature. Then again, as pointed out by Tolman (8), the 
coal-tar colors are frequently contaminated with powerful mineral 
poisons, such as arsenic, copper, tin, lead, and zinc, which are intro- 
duced as impurities in the process of manufacture. It has been 
established further that many of the coal-tar dyestuffs are poisonous 
and that still others not very actively poisonous are nevertheless suffi- 
ciently so to interfere with the action of the digestive ferments. 
For example, Houghton (9) found that annatto diminished the di- 
gestibility of casein and egg albumen by pepsin. For further 
information regarding the toxicity of the coal-tar dyes the following 
authorities should be consulted: Weyl (10), Weber (11), Winogra- 
dow (12), Gudeman (13), Chlopin (14), and Meyer (15). 
Preservatives . — We have seen that milk is subject to many changes, 
principally those resulting from the life and growth therein of micro- 
organisms. Indeed, it is one of the most perishable of foodstuffs, and 
it is only by exercising the most scrupulous cleanliness in the handling 
of it and by keeping it at low temperatures, generally below 50° F., 
that it can be preserved a sufficiently long time to be delivered to 
the consumer in a fresh condition. This has resulted in the practice 
on the part of dairymen of adding to the milk small amounts of 
various antiseptics and germicides, which are supplied to the trade 
under the general name of milk preservatives. The effect of such 
substances is to destroy or at least hinder the growth of all micro- 
organisms which the milk may contain, and thereby retard the 
souring of the milk; and to prevent or at least delay the lactic-acid 
fermentation of milk is the principal object to be attained through 
the use of such substances. Among the various substances which 
have been employed as milk preservatives may be mentioned the 
following : 
Common salt, sodium bicarbonate, formaldehyde (solutions of 
which are supplied to the dairyman under the trade name of “ Freez- 
ine”), borax and boric acid (solutions of the latter once sold under 
the name of “Aseptine ”) , salicylic acid, benzoic acid, hydrogen 
peroxide, certain fluorides, potassium dichromate, etc. Of these 
substances formaldehyde, boric acid and borax, and sodium bicar- 
bonate have probably been the most frequently employed as milk 
preservatives. In certain localities in Europe the addition of alkali 
chromates to milk was at one time a common practice, and Budde 
(16) has proposed a method for the sterilization of milk by the action 
of hydrogen peroxide at a moderately high temperature, viz, 52° C. 
1414— Bull. 56—09 25 
