1820.] Royal Academy of Sciences. 379 



Other metals, reduced in the same manner, produced the same 

 appearances. From this he concludes, that a part of the alkali 

 which he used combined in a metalhc form during the operation 

 with the antimony, and decomposed the water to return to the 

 state of oxide ; but he has of course been also obliged to con- 

 clude, that the presence of a metal is favourable to the reduction 

 of the alkali, as otherwise it would not have taken the metallic 

 form in so low a temperature. 



We mentioned last year some experiments of MM. Chevillot 

 and Edouard upon that singular combination of manganese and 

 potash which is called the mineral cameleon, upon account of 

 the facility with which its colour may be changed several times 

 successively. 



These young chemists have continued their labours, and have 

 discovered that soda, barytes, and strontian, will yield different 

 sorts of cameleons, by uniting, like potash, with the oxide of 

 manganese and absorbing the oxygen from it ; but, confining 

 their principal attention to the species of cameleon formed by 

 potash, in which the alkali is perfectly neutral, and which is of 

 a fine red colour, they have found that those bodies which are 

 very combustible act very energetically upon it, that they decom- 

 pose it, and frequently take fire together with a strong detona- 

 tion : phosphorus even produces a detonation by simple contact. 

 On the other hand, this red cameleon, exposed to fire, is decom- 

 posed, and yields oxygen, black oxide of manganese, and green 

 cameleon, in which potash is in excess . 



They conclude from these facts, that in the formation of the 

 cameleon, the result of the intervention of the oxygen is a further 

 oxidizement of the manganese, and the conversion of it into a 

 true acid; so that the cameleon is a manganesiate of potash. 

 The red cameleon in particular, being a perfectly neutral manga- 

 nesiate, and the green, a manganesiate with an excess of alkali. 

 Still, however, they have not been able to insulate the acid 

 whose existence they admit ; but they have made numerous 

 experiments which they imagine to confirm the opmion they pub- 

 lished last year, that the green cameleon only differed from the 

 red by having more alkali in its composition. 



When acids are poured upon the green cameleon, or an alkali 

 upon the red, they are equally changed from one colour to the 

 other ; even boiling and agitation are sufficient to disengage the 

 excess of potash in the green cameleon, and to change it into 

 red. Many acids also, when used in excess, decompose the 

 cameleon entirely, by taking the potash from it, disengaging the 

 oxygen, and precipitating the manganese in the state of black 

 oxide. Sugar, gums, and several other substances, capable of 

 taking away the oxygen, also decompose the cameleon; and an 

 exposure to the air produces a similar effect, which these authors 

 ascribe to the foreign particles floating in the atmosphere, and 



