388 Foreign and Miscellaneous Intelligence. 



cording to Dr. Thomson, the carbonate of bismuth is a triscarbonate, 

 similar in constitution to the subnitrate and submuriate above. 



Upon decomposing the subnitrate and submuriate of bismuth by 

 alkali, they yield oxide of bismuth ; that, in the first case, is always 

 yellow, but in the second it varies much in colour, being frequently 

 greyish-black and even deep bluish-black. The cause of these varia- 

 tions has not been discovered, nor even the circumstances which 

 ensure a dark coloured preparation. It is not due to sulphu- 

 retted hydrogen or other impurities, nor to difference of composition. 

 When the black oxide was heated on platina foil, it lost neither 

 weight nor colour ; but, being melted, it became yellow : the cause 

 is probably, therefore, in some difference of aggregation ; and may 

 in that respect be analogous to the differences of colour, which can 

 be induced, by various means, on chloride of silver *. 



17. ON THE REACTION OP PERSALTS OF IRON AND NEUTRAL 

 CARBONATES. 



M. Soubeiran has experimentally investigated this action, and arrived 

 at the following conclusions : i. When salts of the peroxide of iron 

 are decomposed by neutral carbonates, they yield a carbonate of the 

 peroxide equally neutral : this carbonate is soon destroyed to pro- 

 duce a double salt, formed of the neutral alkaline sulphate and the 

 subsulphate of iron : this new salt is also easily decomposed, and 

 yields a new sulphate of iron heretofore unknown, and containing 

 thrice as much base as the neutral salt : a feeble alkali in excess 

 precipitates another subsalt, which chemists have not before noticed, 

 and which is a true double salt, composed of the subsulphate of iron 

 and hydrated oxide of iron. ii. That the aperient saffron of Mars 

 is a hydrate of the peroxide of iron, containing 3 atoms of water 

 mixed with variable and accidental quantities of sesqui-subcarbonate 

 of iron, and sometimes neutral carbonate of iron f. 



18. ON THE RELATIVE ACTION OF DILUTED SULPHURIC AciD AND 



ZINC. (M. A. de la Rive.) 



Whilst engaged in experiments on the construction of the voltaic 

 pile, M. de la Rive was struck more particularly with a fact which 

 has often been observed by chemists, but has never received its proper 

 explanation. If zinc, purified by distillation, be plunged into dilute 

 sulphuric acid, it is scarcely attacked, especially at first ; it produces 

 but a small quantity of bubbles of hydrogen, and these succeed each 

 other very slowly ; but zinc of commerce, placed in the same cir- 

 cumstances, produces an enormous quantity of hydrogen, with an 

 effervescence and vivacity well known to those who have prepared 

 this gas. 



* Phil. Mag. N. S. viii. p. 406. 

 f Journ. de Pbarra. 1830, p. 535. 



