172 Miscellaneous Intelligence. 



§ II. Chemical Science. 



1. Application of a high Temperature to the Evaporation of 

 Liquids. — A maker of chloride of lime consulted M. Longchamp 

 on the means of vaporizing a large quantity of muriatic acid, and 

 the latter recommended a tube of platina. In a trial, one kilo- 

 gramme (2.21 lbs.) of acid was vaporized in a tube 3 lines in 

 diameter, and heated for 8 inches of its length. A larger apparatus 

 was then made, consisting of a tube 2 inches in diameter, and 42 

 in length ; but as 4 inches were external at one end, 2 at the other, 

 and 4 were included in the sides of the furnace, only 32 inches in 

 length were heated, equal to a capacity of 96 cubical inches. With 

 this, 1 kilogramme of acid was evaporated in a minute, or 1500 

 kilogrammes in 24 hours. A trial was made to support the platina 

 tube by one of cast iron, but the latter fused, and caused the former, 

 which had become very brittle at the fusing part, to break ; being, 

 however, cut and repaired by soldering with gold, it was as good 

 and effectual as at first. 



From the effects produced, M. Longchamp concludes, that at 

 high temperatures the evaporation is not in proportion to the 

 heated surfaces, but in proportion to the capacity heated ; that in a 

 vessel heated to redness, it is 8 times greater than at the usual 

 temperature employed, and that tubes of platina may be used to 

 vaporize large quantities of muriatic acid. — Ann. des Sciences. Bull. 

 Univ. A. xi. 353. 



2. On the Specific Heat of Gases. — In a memoir on the specific 

 heat of gases published some time since, MM. de la Rive and 

 Marcet gave their results and conclusions, the latter being, that all 

 gases had the same specific heat. The results have been a little 

 objected to, as having been obtained upon quantities of gas too 

 small, and the authors have therefore repeated their experiments 

 on a larger scale, and given the full detail in a memoir published in 

 the Bibliotheque Universelle, N.S. xli. p. 37. We shall probably 

 return to this paper ; in the mean time we give the conclusions, 

 which are precisely the same as in the former case, namely — 



i. That at the same pressure, and in the same volume, all the 

 gases have an equal specific heat. 



ii. That in the same volume the same gas has a smaller specific 

 heat, in proportion as it is subjected to a smaller pressure. 



3. Artificial Preparation of Ice. — After numerous trials made by 

 M. B. Meijlink with different salts, for the purpose of converting 

 water contained in a tin vessel into ice, during their solution, he 

 ultimately gave the preference to a mixture of 4 ounces nitrate of 

 ammonia, 4 ounces sub-carbonate of soda, and 4 ounces of water. 

 This mixture, in three hours, produced 10 ounces of ice ; whilst with 

 the mixture of sulphate of soda and muriate acid, he obtained ice 

 only after 7 hours. 



