IS History of physical Science from [July, 



but dissolves little of the oxide. But if the acid be decanted off, 

 and a sufficient quantity of water be poured upon the residual 

 oxide, a complete solution is effected. Muriatic acid throws it 

 down again, 'and the precipitate, which is a neutral muriate, 

 may be again dissolved in pure water. This aqueous solution 

 coagulates when heated, how dilute soever it may be. The oxide 

 from the liquor of Libavius dissolves completely in muriatic acid, 

 and is not precipitated by an addition of that acid in excess. 

 The liquor of Libavius dissolves in concentrated muriatic acid 

 just as well as in pure water. — (Ann. de Chim. et de Phys. 

 v. 149.) 



6. Chameleon Mineral. — This name has been given by chemists 

 to a mixture of black oxide of manganese and caustic potash 

 fused together in a crucible. The mass is green. At first it 

 forms a green solution in water, and this solution passes through 

 the suite of colours constituting the coloured rings into red. 

 Some valuable observations on this compound, first pointed out 

 by Scheele, have been made by Chevreul (Ann. de Chim. et 

 de Phys. iv. 42); and by MM. Chevillot and Edwards (ibid, 

 p. 287). Chevreul showed that it existed in two states ; namely, 

 the green and the red, and that it is a compound of pure oxide 

 of manganese and potash. Chevillot and Edwards ascertained 

 that it might be formed by means of any pure oxide of manga- 

 nese and potash; that during its formation, oxygen gas is 

 absorbed, and that this absorption is a maximum when the 

 quantity of the oxide of manganese is equal to that of the potash. 

 The green colour is most beautiful when the quantity of potash 

 considerably exceeds that of the manganese. These gentlemen 

 inform us that they succeeded in obtaining the red cameleon 

 mineral in crystals by evaporating its solution. Their method 

 was to form the chameleon by heating together equal weights of 

 pure potash and black oxide of manganese. The solution of 

 this in water is decanted off to get rid of the precipitate ; it is 

 then evaporated rapidly till it begins to deposit crystals. The 

 liquid is then kept in a heat below that of boiling water. Red 

 needles are deposited, varying in length from two lines to eight. 

 These crystals are permanent in the air, and give a very strong 

 red colour to water. 



These observations are curious, but they do not make us 

 acquainted with the real nature of this singular compound. 



7. Platinum. — Vauquelin has succeeded in forming sulphuret 

 of platinum, and has ascertained the characters of this com- 

 pound. Happening to prepare a sulphuret of soda in a platinum 

 crucible, he observed, on dissolving the sulphuret in water, a 

 residuary black matter in needles. When this matter was heated 

 in the open air, it gave out the odour of sulphurous acid, and 

 left metallic platinum behind. It was, therefore, sulphuret of 

 platinum, and had been formed by the action of the sulphuret of 

 •otla on the crucible. He formed the same sulphuret by heating 



