222 PROCEEDINGS OF THE AMERICAN ACADEMY 



that substance may be written. To prove that oxygen is absorbed dur- 

 ing the formation of manganate of potash from caustic potash and black 

 oxide of manganese, is therefore not at all to the purpose ; the only 

 question is, Can any manganate be formed without absorption of oxygen ? 

 This question the experiments of Mitscherlich and BeketoiF answer in 

 the aflBrmative. But if manganate of potash is formed from caustic 

 potash and black oxide of manganese without any addition of oxygen, 

 how is the fact of its non-fox'mation in an atmosphere of nitrogen, as 

 proved by Chevillot and Edwards, to be accounted for. "We have i*e- 

 peated the experiments of Chevillot and Edwards with a somewhat dif- 

 ferent appax'atus. A combustion-tube of small diameter was nearly 

 filled with copper turnings, and beyond the copper a platinum boat con- 

 taining a mixture of caustic potash and peroxide of manganese was 

 inserted. The tube was then connected with an aspirator, and a slow 

 current of air was drawn through the hot copper. When time enough 

 had elapsed to secure the complete filling of the tube with nitrogen, the 

 platinum boat was heated gradually up to dull redness without produc- 

 ing a trace of the green manganate. When the tube had cooled, the 

 contents of the boat was a fused, brownish mass. Another experiment, 

 however, showed conclusively that the non-appearance of the green 

 manganate is accounted for by the fact that this manganate cannot ex- 

 ist in an atmosphere of nitrogen at such a temperature. We prepared 

 some manganate of potash in a platinum boat by fusing a mixture of 

 carbonate of potash and black oxide of manganese in the air, and then 

 heated this boat with its contents in an atmosphere of nitrogen by 

 means of the apparatus just described. At a temperature very much 

 below a red heat every trace of the green manganate disappeared, and 

 when the tube was cool the appearance of the contents of the boat was 

 that of a fused, brownish mass, precisely like that described above in 

 the former experiment. Repetitions of the experiments fully confirmed 

 these results, which perhaps ought to have been anticipated, since it 

 seems more than probable that nitrogen would be oxidized in contact 

 with a hot manganate. Similar experiments with an atmosphere of 

 carbonic acid led to the same negative results. It must be borne in 

 mind that our present purpose is merely to show the fallacy of the in- 

 ferences which Chevillot and Edwards di'ew from their experiments, 

 which were made at an uncertain but high temperature. We by no 

 means wish to assert that it is impossible to obtain the green manganate 

 of potash from a mixture of caustic potash and black oxide of manga- 



