M. R. Sclineider on the Equivalent of Manganese. 269 



my laboratory. In these experiments the amount of water was 

 determined which a given quantity of pure and most carefully- 

 prepared niangano-manganous oxide furnished when reduced 

 in a stream of dry hydrogen, free from air, to manganous oxide. 

 if a denotes the quantity of mangano-manganous oxide, b the 

 quantity of water obtained, the equivalent of manganese is calcu- 

 lated from the equation ^ ^ / 32(g— 4 x 0-8889 b)\ 

 ^ ~^\ 4^(>8889^6 / • 



It must be admitted that this method does not wholly satisfy 

 the strict conditions which may be demanded for the determina- 

 tion of an equivalent. It is clear that a small error in the esti- 

 mation of the water appears as a comparatively great one iu the 

 equivalent number. IS^evertheless we may expect an approxi- 

 mately correct value from a long series of experiments performed 

 with accuracy. 



The apparatus in which the reduction was effected, received 

 such an arrangement that the narrow finely drawn-out end of 

 the reduction tube passed in an oblique direction deep into the 

 chloride of calcium tube destined to receive the water. This 

 limb of the reduction tube, in order to prevent any loss of man- 

 ganese, was filled for 3-4 inches with a loose plug of previously 

 ignited asbestos. The ignition of the oxide in the current of 

 hydrogen was continued until the formation of water had entirely 

 ceased, and the contents of the tube of reduction had assumed a 

 pure green colour. No weighing was made of the residual sub- 

 oxide, as the degree of compactness acquired by the substance 

 at the temperature to which it can be subjected iu a glass tube, 

 is not sufficient to prevent an immediate partial oxidation when 

 it is exposed to the air*. 



Of nine experiments in which the above process was employed, 

 and in which the quantities of mangano-manganous oxide varied 

 between 1"6 and 11'6 grms., I here adduce the six which gave 

 the most accordant results : — 



grins. g''™. 



I. 4-149MnO,Mn203 gave 0-330 HO, hence equiv. 27-052 

 II. 4-649 „ 0-370 „ 27-029 



III. 6-8865 „ 0-5485 „ 26-999 



IV. 7-356 „ 0-5855 „ 27025 

 V. 8-9445 „ 0-7135 „ 26942 



VI. 11-584 „ 0-9225 „ 27-005 



* By the application of a higher temperature, it is possible to make the 

 miboxide of manganese insensible to the oxygen of the atmosphere. On 

 heating some for four hours at a white heat in a porcelain tube in a stream 

 of hydrogen, it appeared, without having undergone any further reduction, 

 to be strongly agglomerated ; and even iu a state of very fine powder it 

 preserved its green coloui- unaltered in the air. 



