484 
DECOMPOSITION OF MILK. 
certainly demonstrate the great advantage attending the use 
of the colour-developing substances in the solid state. The 
experiments, it will be observed, are strictly logical and 
comparative. The distilled water added to the acid solution 
of the alkaloid, or to the colour-developing substance, was 
the only element of variation in the two series of experi¬ 
ments. 
That the indistinct, or wholly negative, results obtained when 
distilled water is added are not due to mere dilution, or in¬ 
crease in the quantity of liquid present, is shown by the 
following experiment:—I placed five equal drops of the same 
solution of strychnia in sulphuric acid (l-200th grain in the 
drop) on each of three porcelain slabs. I made no addition 
to the first drop, but added to the second drop one drop of 
strong sulphuric acid ; to the third, two drops ; to the fourth, 
three drops; and to the fifth, four drops. I then added to 
each spot on the first slab an equal fragment of bichromate 
of potash; to each spot on the second slab, an equal frag¬ 
ment of peroxide of manganese; and to each spot on the 
third slab, an equal fragment of the permanganate of potash. 
The reactions were perfect and characteristic in each case, 
the colours differing only in depth of tint, but not in propor¬ 
tion to the degree of dilution. The peroxide of manganese 
was remarkable for the duration of the colours, and the per¬ 
manganate of potash for their brilliancy. 
Having now, as I believe, shown the superiority of the 
colour-developing tests in substance to the same test in solu¬ 
tion, and demonstrated the disadvantage of introducing into 
the colour-tests the element of dilution with water, 1 shall 
reserve for another communication the question of the effect 
of the quantity of the colour-developing substances on the 
success of the colour-tests, as well as the answer to the three 
remaining questions. 
(To be continued.) 
DECOMPOSITION OE MILK. 
Fresh cow’s milk exposed to the air absorbs oxygen, and 
disengages carbonic acid, the volume of carbonic acid disen¬ 
gaged being greater than that of the oxygen absorbed. This 
exchange of gas takes place very rapidly after twenty-four 
hours; and milk in contact with a volume of air greater than 
its own takes up all the oxygen in three or four days. In an 
atmosphere of pure oxygen, the absorption of this gas and 
the disengagement of carbonic acid, takes place still more 
rapidly. The carbonic acid, says Hoppe, is formed at the 
