l68 THE ENERGY OF THE LIVING PROTOPLASM. 



aluminium chloride in the synthesis of hydrocarbons, that of 

 zinc chloride in the transformation of glycol into aldehyde, and 

 the accelerating action of iron and copper salts upon the 

 oxidation of phenol by peroxide of hydrogen. <I( 



The genuine katalytic actions may be divided into three 

 groups : 



1. Katalysis by labile organic compounds, 



2. Katalysis by mineral acids, caustic lyes, and certain salts, 



3. Katalysis by finely divided metals. 



In regard to the first group maybe mentioned the conversion 

 of dicyanogen into oxamide by a dilute solution of ethylic 

 aldehyde, a reaction observed by Liebig ; the transformation of 

 thiourea into the isomeric ammonium thiocyanate by an alcoholic 

 solution of ethyl nitrite {Clam) ; the facilitating action of acetic 

 ester upon the combination of hydrocyanic with hydrochloric acid 

 (Claisen and Mathews). Malei'c acid transforms ketazines into the 

 isomeric pyrazolines with liberation of heat, (2) whilst fumaric 

 acid can only accomplish this at a temperature of 100. 0 To this 

 group of actions belongs evidently not only the action of the 

 living cells, but also the action of the enzymes, which have a 

 high degree of lability and betray, by their easily passing into an 

 inactive state, as well as by their proteic nature, a certain rela- 

 tion to the proteids of the living protoplasm. The fact that 

 dilute formic aldehyde destroys their activity even in perfectly 

 neutral solution at the ordinary temperature, makes the presence 

 of highly labile amido-groups probable. (3) 



(1) Chem. Centralbl. 1885, p. 224. In certain cases the apparently katalytically 

 acting substance is mainly a suitable medium to bring two compounds into more 

 intimate contact with each other, or by combining with one of two compounds pre- 

 sent to help to loosen somewhat certain affinities in the molecule, and thereby bring 

 about combination with the second compound. 



(2) Curtius and FoerstcrVuig, Ber. D. Chem. Ges. 27, 770. F. Stohmann deter- 

 mined the thermic value of malei'c acid to be 326.3 cal. and that of fumaric to be 319.7 ; 

 the latter possesses, therefore, less energy than the former. Stohmann recognised by 

 direct experiment, in determining with great exactness the heat of combustion, that 

 labile compounds always have a higher thermic value than the isomeric stable ones. 



(3) O. Loav, Jahresber. f. Thierchem. 1888. I have observed also that a solution 

 of prussic acid of 25 °/ 0 destroys in twelve hours the diastatic but not the pro- 

 teolytic enzyme of the pancreas (Pfli'tg. Arch. 27, 208). Cf. also Schcir and Fichter, 

 Jahresber f. Thierchem. ,5, 269. Certain bacterial enzymes are rendered inactive by 

 sulphuretted hydrogen (Fermi and Bcrnossi . 1894). Chloroform retards enzyme-action 

 (Salkozvski). According to Arsonvalc (1894) enzymes are rendered inactive by a 

 temperature of — I50°C. 



