290 
Milk. 
into lactic acid or into fruit-sugar, which in its turn enters into 
alcoholic fermentation, producing carbonic acid and alcohol. 
Under favourable circumstances milk may thus be fermented, 
and converted into an intoxicating alcoholic beverage. It has, 
however, under the influence of partially decomposed casein, 
which acts as a ferment, a greater tendency to turn acid than to 
enter into alcoholic fermentation, especially when the tempera- 
ture of the air is high. 
Sugar of milk, or lactose, contains, when pure, in 100 parts — 
Carbon 40-00 
Hydrogen t)'6() 
Oxygen 53-34 
100-00 , 
These numbers correspond to the formula Cjg H,2 0,g Avhich 
is assigned to it by chemists. It will be seen that it is free from 
nitrogen, and contains hydrogen and oxygen in the same relative 
proportion in which these two elements occur in water. 
Sugar of milk may therefore be represented to be a carbon- 
hydrate, or compound of carbon with water only. 
Lactic acid and fruit-sugar, though widely differing in thoir 
physical and chemical properties, nevertheless contain in 100 
parts precisely the same amount of carbon, hydrogen, and oxygen 
as sugar of milk. 
Under the influence of casein-ferment lactose is changed into 
"lactic acid in the simplest possible way. Without gaining or 
losing anything, 1 equivalent of lactose, C,2 Hjg 0,2, splits into 
2 equivalents of lactic acid, Cg H5 O5, + HO ; for 
C,2 H,2 0,2 = 2 (C, H, 0„ HO) 
1 equivalent of lactose = 2 equivalents of lactic acid. 
4. Mineral Matters (Ash of Milk). — When milk is boiled 
vdown, and the dry matter burnt, it leaves from J to J per cent, 
of a whitish ash, which consists mainly of phosphate of lime 
-and magnesia (bone earth), and the chlorides of potassium and 
sodium, besides a small quantity of phosphate of iron and some 
free sod;'.. 
The relative proportions of these several substances yielded by 
1000 lbs. of the milk of two different cows, as given by Haidlcn, 
are as follows : — ■ 
lb3. ' lbs. 
rhospliate of lime 2-31 3-44 
rhosphate of mactTicsia '42 '64 
I'hospliate of peroxide of iron '07 "07 
'Chloride of jiotassiiun ]-44 1-83 
Chloride of sodiiun '24 "34 
Pree .soda "42 •45 
i-90 0-77 
