MILK. 
415 
will be, I think, no doubt on the part of those who try it; 
and it has this important advantage over other methods, that 
excepting the copper, the purity of which is to be tested, and 
hydrochloric acid, the purity of which may be easily deter¬ 
mined by a preliminary experiment, no chemical is used. 
It is equally applicable to the detection of minute traces of 
arsenic in the sulphate and all the salts of copper, soluble or 
indisoluble. It is only necessary to distil them with a suffi¬ 
cient quantity of pure hydrochloric acid. I had in vain 
sought for evidence of arsenic in some sulphate of copper by 
the use of Marsh’s process; but on distilling only ten grains 
of the crystals with hydrochloric acid, chloride of arsenic 
was obtained in the receiver, and the presence of the poison 
was satisfactorily proved. In the course of the Smethurst 
analyses in July, 1859, Mr. Brande and Dr. Odling adopted, 
at my suggestion, this method of analysing some sulphate of 
copper pills for arsenic, and they both expressed their satis¬ 
faction with it as a safe and delicate process. 
(To he continued .) 
MILK. 
We might fairly expect that milk would be exceedingly 
rich in nourishing materials, since it is the first food tasted by 
all ranks of mammalian animals, and the food upon which 
they make most progress in the shortest time. The con¬ 
stituents of milk are much the same in all species of 
mammalian animals, the difference in the qualities of milk 
depending on slight differences in the proportions of the 
constituents. As cow’s milk is that almost exclusively 
employed in this country for the preparation of dairy pro¬ 
duce, the following remarks apply more particularly to this 
kind of milk. We shall better understand these remarks 
by first observing the general composition of milk, which 
may be represented as follows :— 
COMPOSITION OF MILK. 
Cow’s Milk. Ass’s Milk. Human Milk. Cream. 
Water.87*04 
Caseine.4"26 
Butter.3"13 
Sugar.477 
Mm. constituents . *80 
100-00 
91-65 
88-80 
62-50 
1-80 
3-82 
5-62 
1-12 
3-04 
30-58 
6-03 
4*20 
trace. 
*40 
T4 
1-30 
100-00 
100*00 
100-00 
