Intelligence and Miscellaneous Articles, 387 



I must here mention a circumstance which may not be without 

 some interest for the geologist. Mineralogists are not agreed as to 

 the composition of the arseniate of lime, formerly called pharmacolite, 

 which would appear to lead to the opinion that several natural com- 

 pounds of lime and arsenic acid exist. M. Dufrenoy is, for this 

 reason, inclined to the opinion that this compound is a product of 

 the decomposition of arseniferous minerals, and that it frequently 

 contains an excess of base and hygrometric water which entirely 

 alter the proportions. I will here add, that all the natural crystals 

 are effloresced, and present the appearance of the crystals of double 

 arseniate of lime and ammonia which have lost their ammonia and a 

 part of their water of crystallization when they have been exposed to 

 the atmosphere'; however, the composition of these two kinds of 

 crystals is not the same ; the natural arseniate, irrespective of the 

 water, is composed of 2 equivs. of lime and 5 equivs. of arsenic acid, 

 or of 1 equiv. of the former and 2 equivs. of the latter, while the 

 arseniate of lime, as I have prepared it, contains 2 equivs. of lime 

 and 1 equiv. of arsenic acid. During the decomposition of the me- 

 tallic arseniates it may happen that alkaline arseniates are formed, 

 which reacting upon carbonate of lime, give rise to the formation of 

 arseniate of lime. 



The double arseniate of lime and ammonia, and consequently the 

 arseniate of lime, may likewise be obtained by digesting, in a solu- 

 tion of arseniate of ammonia (10°), plates of sulphate of lime ; after 

 some months, acicular crystals are seen upon the surface of the 

 mineral, which, according to all appearances, have the same chemical 

 composition as the double arseniate above described. 



In conclusion, I will mention some preparations which are not 

 without interest. When a calcareous mineral, coated with sub- 

 nitrate of copper, is allowed to react upon a saturated solution of 

 neutral or bichromate of potash, there are obtained, in the first 

 place, chromate of copper in microscopic crystals of a clear green 

 colour, and secondly, a chromate of the same base also, in micro- 

 scopic crystals, but of a brownish red colour. 



Crystallized cyanide of copper may be obtained in the same man- 

 ner; it is of a red colour. — Comptes Rendus, January 1853, 209. 



ON THE TEMPERATURE PRODUCED BY THE COMBUSTION Of 

 CARBON IN THE AIR. BY H. DEVILLE. 



It is well known that near the tuyeres of blast furnaces, a very 

 elevated temperature is developed, which M. Ebelmen considers to 

 be equal to the meking-point of platinum. Some experiments made 

 in the course of an investigation altogether different, have led me to 

 believe that the heat developed during the combustion of carbon is 

 capable of producing eiFects much more energetic and comparable 

 with those obtained by means of a mixture of hydrogen and oxygen. 

 Thus, by a suitable arrangement of the furnace, and with the pro- 

 per kind of carbon, it is possible to melt and even to volatilize plati- 

 num and to melt pure silica*. These results, and the simplicity of the 



* M. Deville exhibited to the Academy a crucible made from platinum 



