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ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 109 
Other papers of much interest in the elucidation of the peroxidase 
reaction :— 
Fenton, Zrans. Chem. Soc., 65, 899-910 (1894). 
Euler and Bolin, 7. f. physiol. Chem., 5'7, 80-98 (1908). 
Herzog and Meier, 7. /. physiol. Chem., 73, 258-262 (1911). 
Bach and Chodat, Berichte d. Chem. Ges., 3'7, 1342-1348 (1904). Arch. d. Sciences 
Phys. et Nat., Geneva, 37, +77. 
Arnost, 7. f. Unters. Nahr. wu. Genussm. (1905), 10, 309. 
Bertrand, C. Rendus. 124, 1355 (1897). 
Kastle and Porch, J. of Biol. Chem., 4, 301 (1912). 
Kooper, 7. Unters. Nahr. vw. Genussm., 23, 1 (1912). 
Leffmanu, Analyst, 1898, p. 85. 
Sames, Wilchw. Zentralb., 6, 462 (1910). 
Sarthou, Journ. de Pharm., 3, 49 (1911). 
Seligmann, 7. f. Hyq., 50. 97 (1905). 
Utz, 7.7. angew. Chem., 16, 871 (1903).  Oesterr. Chem. Ztg. (1904), p. 916. 
Waentig, 47d. a. d. kaiserl. Gesundh., 26, 464 (1907). 
- Weber, Milchzty. (1902), pp. 657, 673. 
Wirthle, Chem. Zig. (1903), p. 432. 
(b) Reductase. 
It has long been known that if methylene blue be added to milk, 
the blue colouration produced could often be destroyed by incubating 
the milk for a while, the time required varying with the samples of 
milk taken. ‘The action is recognised asa bacterial one, and great 
efforts have been made to utilise it to measure the bacterial content 
of milk, but owing to the fact that only some, and not all, of the 
bacteria in milk are concerned in the reaction, the method was 
found very unreliable. 
Schardinger (Zeit. Unters. Nahrungs- und Genussmittel 5, 1113— 
~ 1121 (1902) ) made some notable observations on the milk-reduction 
of methylene blue, establishing the following facts :— 
(1) Fresh milk alone does not reduce methylene blue. 
(2) Fresh milk to which an aldehyde (e.g. formaldehyde) has 
been added reduces methylene blue to the leuco or 
colourless base. 
(3) This decolouration does not take place if the milk has been 
boiled. 
(4) lf bacterial development be permitted, there is no need to add 
aldehyde to milk to obtain the reduction of methylene blue. 
The reaction in the absence of aldehyde is now termed the “ direct 
reductase reaction,” and in the presence of aldehyde, the “indirect 
reductase reaction.” 
Shardinger’s M.B. reagent is obtained by diluting 5cc. of a 
saturated alcoholic solution of methylene blue with 195cc. of water. 
His F.M.B. reagent contains 5cc. saturated alc.; methylene blue + 
5ec. of 40 per cent. formaldehyde + 190cc. water. In each case one 
uses lec. of the reagent to 20cc. of milk warmed to 45° to 50° C. 
The specific enzyme causing the reaction is termed “ualdehyde- 
reductase” or ‘“ formaldehydase.” 
It is inferesting to note that analogous reactions in inorganic 
chemistry are obtained, using the colloidal solutions of metals of the 
platinum group. Thus aqueous solutions of hypophosphites are 
oxidised on the addition of finely-divided palladium :— 
< H;P0,+2H:,0 H3P03+ H,+H 20. 
