Progress of Foreign Science. 147 



ing heat, corrosive sublimate and deuto-sulphate of mercury are 

 formed. No muriatic gas is evolved. On heating sulphur and 

 calomel together, he obtained muriatic acid gas, indicating, of 

 course, the presence of hydrogen in the former body. The two 

 sublimed muriates of antimony and bismuth in a concrete state, 

 are not affected at ordinary temperatures by sulphuric acid! 

 No action occurs between muriate of silver and sulphuric acid 

 without heat. M. Vogel says, that it is only the muriates, 

 whose metals are capable of decomposing water, such as iron, 

 zmc, and manganese, which occasion an effervescence in the 

 cold with sulphuric acid, and that all the muriates whose bases 

 do not decompose water, make no effervescence with sulphuric 

 acid without the aid of heat. 



IV. We promised in the last Number to notice M. Robiquet's 

 speculations on the constitution of ferro-prussiate of potash. 

 " Mr. Porrett," says he, " after having varied much with 

 regard to the composition of this salt, regarded it in his last 

 analysis, as formed by the union of one atom of prussic acid, 

 two atoms of carbon, and one atom of iron; whilst, according 

 to my experiments, it should be considered as a combination 

 containing the elements of the hydrocyanic acid, and of the 

 cyanide of iron, just as we conceive alkohol to be formed of 

 water and defiant gas. I had inferred, as a consequence of 

 this manner of viewing the acid, that the triple prussiates 

 might themselves be considered as a double combination of 

 a hydrocyanate, differing for the different prussiates, and of a 

 cyanide of iron, constant for the whole. M. Berzelius has 

 just published a very extensive memoir, in which he labours 

 especially to disprove the existence of this acid. The very- 

 numerous analytical experiments which he has made, to deter- 

 mine the composition of the triple prussiates, have led him to 

 admit that they were all formed of one atom of cyanide of iron, 

 and of two atoms of the cyanide of another metal. The main 

 purpose of M. Berzelius is to establish, that the acid product 

 which Mr. Porrett and I obtained, in decomposing the triple prussi- 

 ates, is not a peculiar acid,but merely an acidulous hydrocyanate 

 of the protoxide of iron ; so that this hydrocyanate, in combining 

 with another base, forms a double hydrocyanate susceptible of 

 conversion, by mere drying, into a double cyanide." It is known 

 that in Prussian blue, the portion of iron which supplants the 

 variable base (potassium or potash, for example), is in the 

 state of peroxide. If this combination be put in contact for 

 a sufficient time with sulphuretted hydrogen water, there 

 is a partial deoxidizement of the peroxide, and this retro- 

 gradation cannot take place without a proportionate diminution 

 of its capacity of saturation, and of consequence also, without 

 a proportionate quantity of the acid being set at liberty. If M. 



