ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 111: 
Rémer and Sames (Zei/. f. Unters. Nahr-u. Genussm., (20), 
1 (1910) ) showed that milk which failed to respond to 
the Schardinger test would do so if a small quantity (less 
than 1 per cent.) of ferrous sulphate were added. ‘The 
ferrous sulphate solution must not be boiled. 
. BIBLIOGRAPHY. 
a Arup, Analyst, Jan. (1918). 
a Bach, Biochem. Zeit. 31, 443 (1911) and 38, 282 (1911). 
Bertin-Sans and Ganjoux, Rer. d' Hyg. 36, 258 (1914). 
Burri and Kursteiner, Milchw. Zentralb. 8, 40 (1912). 
Cathcart and Hahn, Arch. f. Hyg. 44, 295 (1902). 
Fred, Centralb. f. Bakt. ii. (1912) 35, 17 ; Analyst, 38, 62 (1918). 
Jensen, Rev. gén. du Lait. §, 33, 56, 85 (1906). 
j 
| Barthel, Zeit. f. Unters. Nahr- u. Genussm. 21, 513 (1911); Analyst, 36, 346 (1911). 
Lagane, Rev. d’ Hyg. 36, 222 (1914). 
Neisser and Wechsberg, Miinch. med. Woch. 4'7, 1241 (1900). 
Paal and Gerum, Berichte d. chem. Gesell. 41, 805 (1908). 
Seligmann, Zeit. f. Hyg. 58, 1 (1908). 
Shroeter, Centralb. f. Bakt.ii. 32, 181 (1911). 
Siegfeld, Zeit. f. angew. Chem. 16, 764 (1903). 
Smidt, .Arch. f. Hyg. 58, 313 (1908). 
Somerfeld, Hyg. Centralb 4, 1 (1908). 
(c) Catalase. 
This very remarkable enzyme is universally present in cow’s 
milk. It acts on hydrogen peroxide to produce molecular oxygen, 
this result being very unique, since one usually cbtains ‘active’ or 
atomie oxygen when H,02 is decomposed. The generally-accepted 
explanation is that the enzyme attacks two molecules of H20; 
simultaneously, thus :— 
2HOOH=2H,0+0, 
Catalase in milk is estimated by measuring the volume of oxygen 
liberated when a given quantity of H,Q, is added to a given quantity 
of milk. Usually one takes 20cc. of milk and 5cc. of a 3 per cent. 
H.0, solution, using a special apparatus, which is kept in the water- 
bath during the course of the test. 
The catalase is most probably of ‘bacterial action, and its amount 
mcreases when the milk grows stale. Cream contains a larger 
percentage of catalase than the rest of the milk. So far no figure for 
the normal catalase content of milk is agreed upon, though such a 
standard is desirable as an indication of the bacterial content of a 
_ given sample. 
Oxidising agents such as chlorates, nitrates, and hydrogen 
-_ peroxide, and poisonous bodies like HCN or mercuric chloride are 
especially harmful to catalase ; indeed, Euler has shown that a strength 
of 1 in 1,000,000 of HCN reduces the reaction velocity of catalase by 
one half. 
BIBLIOGRAPHY. 
Barthel, Zeit. f. Unters. Nahr- u Genussm. 15, 385 (1908). 
Bier, Maly’s Tierch. 35, 230 (1905). 
Burri and Staub, Zit. 7. Unters Nahr- wu Genussm. 1'7, 88 (1909). 
Chick, Centralb. f. Bakt. ii., '7, 705 (1901). 
Faitelowitz, Milch Centralb. 6, 299, 361 (1910). 
Gerber and Ottiker, Milch. Centralb. 6, 316 (1910). 
Gifforn, Ref. Rev. gén. du Lait, 8, No. 22 (1911). 
