272 M. R. Schneider on Equivalents, and 



the relation between the carbon and manganese in pure neutral 

 manganous oxalate. Inasmuch, however, as the oxides of 

 manganese cannot be reduced to the metallic state on being 

 heated in a stream of hydrogen, the amount of manganese in 

 the salt could only be determined indirectly by estimating the 

 water formed at the same time. From the difference of the sub- 

 stance emploj'ed and the water, the amount of the anhydrous 

 salt was determined ; from the difference between this and the 

 carbonic acid, the weight of the manganese was determined. I 

 have not sought to render the salt perfectly anhydrous previous 

 to its use, because, even had this been possible, the advantage so 

 obtained would have been counterbalanced by the danger of a 

 partial oxidation of the manganous oxide. 



The carbonic acid and water were determined by combustion 

 of the oxalate with oxide of copper, dry air deprived of carbonic 

 acid being passed over the salt. 



Four experiments of this kind gave the following results : — 

 (1) Equivalent of manganese 37-008; (2) 27-028; (3) 27-023; 

 (4) 27015. Mean 27-019, or in round numbers 27-019. 



Schneider has also shown experimentally that oxalate of man- 

 ganese, if heated slowly, gives up all its water without further de- 

 composition. 



The equivalent of nickel was determined in almost a precisely 

 similar manner, and from the mean of three experiments was 

 found to be 29-029. Marignae had found the equivalent of 

 nickel to be 29-20, or 29-64. His methods were the ignition of 

 the anhydrous sulphate and the determination of the chlorine in 

 the anhydrous subchloride. Perhaps the objection to the last 

 method was obviated by Dumas, who exposed the anhydrous 

 chloride for twelve hours at a red heat to hydrochlox'ic acid, and 

 who fouud the equivalent to be 29-5. 



Marchand and Erdmann, by the reduction of the oxide in 

 hydrogen, found the numbers 29-1 and 29-3, the preference 

 being given to the smaller number. 



XLII. On Equivalents, and their Determination in general. 

 By R. Schneider*. 



IT is certainly of great use, and advantageous for the advance- 

 ment of science, to investigate the methodical arrangement 

 which the equivalent weights of the simple bodies show. The 

 endeavours of chemists in this direction, namely the arrange- 

 ment of the equivalent numbers in series, as has lately been 

 ingeniously attempted by Pettenkofer and Dumas, may be 



* Translated by Dr. Guthrie from PoggendorfF's Annalen, No. 8, 1859, 

 ].. C19. 



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