270 M. R. Schneider on the Equivalent of Manganese. 



As the mean of these six experiments the number 27"009; or 

 in round numbers 27, is obtainedj that is, almost exactly a 

 simple multiple of the eqviivalent of hydrogen. 



These experiments were nearly finished when communications 

 were published by several chemists on the equivalent of manga- 

 nese. 



Von Hauer* determined it by reducing anhydrous sulphate 

 of manganous oxide to sulphide of manganese by means of dry 

 sulphuretted hydrogen. By this method (as a mean of nine 

 experiments) he found the amount of oxygen in the sulphate to 

 be 42"39 per cent., and accordingly the equivalent of manga- 

 nese to be 27'5. 



Although it is to be admitted in favour of this number that 

 it coincides almost exactly with that obtained by Berzelius in 

 another manner, still the expeinments whence it is derived are 

 perhaps not entirely free from sources of error. Even if it be 

 admitted that the sulphate of manganous oxide, on being dried 

 at a high temperature with access of air, be not at all affected by 

 the oxygen of the atmosphere, still we must not neglect the fact 

 that the oxysulphide of manganese which is formed, and for a 

 time exists, when sulphate of suboxide of manganese is heated 

 in a stream of sulphuretted hydrogen, obstinately retains a por- 

 tion of oxjrgen in its conversion into sulphide of manganese. 



Arfwedsonf, on heating 100 parts of MnO, MuS in HS, ob- 

 tained only 109'34' parts sulphide of manganese, instead of 

 110"12 or 110'25 parts, which should have been obtained if 

 Mn = 27"5 or 27 respectively. In addition to this, at a high 

 temperature sulphide of manganese itself is very prone to take 

 up oxygen ; hence if the current of sulphuretted hydrogen be 

 not freed most carefully from air, a continuous sovirce of oxygen 

 is furnished. From these considerations I do not think that a 

 method which in the case of cadmium has led to undoubtedly 

 correct results J, is calculated to furnish results of equal excellence 

 when applied to the determination of the equivalent of man- 

 ganese. 



Dumas §, in his well-known treatise on the equivalents of 

 simple bodies, stated that he had determined the equivalent of 

 manganese by reducing in a current of hydrogen artificially 

 prepared peroxide of manganese to suboxide, and that the num- 

 ber 26 was obtained, as is expressly said, " d'une maniere absolue." 

 The detail of the experiments by which this surprising number 

 was obtained were not at first given : their publication was 



* Beiicht der fVien. Acad. JSIath.-naturw. Kl. vol. xxv. p. 124. 

 t PoggendorfF's Annalen, vol. i. p. 50. 



X V. Hauer, Bericht der Wien. Acad. Math.-natur. Kl. vol. xxv. p. 118. 

 § Comptes Rendus, vol. xlv. p. 709. Ann, der Chem, imd Pharm. vol. cv. 

 p. 72. 



