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 LXVI. Intelligence and Miscellaiieous Articles. 



SPECIFIC HEAT OF ELASTIC FLUIDS. 



THIS subject, which has been under investigation at various times 

 by MM. De la Roche and Beraid, Haycraft, De la Rive and Marcet, 

 has been taken up by M. Dulong, who has applied to it a new method 

 of investigation dependent upon the velocity of sound in the different 

 gases. La Place showed that the velocity of the sound in air or other 

 elastic media was importantly influenced and increased above the ex- 

 pected velocity by the heat evolved, as the vibrations producing sound 

 passed through the air ; and M. Dulong, by examining and comparing 

 the sounds produced by different gases, has endeavoured to ascertain 

 whether this element is the same in all of them. He arrives at this 

 general law, remarkable for its simplicity, 1 . That equal volumes of all 

 elastic fluids taken at the same temperature and pressure, when com- 

 pressed or expanded by a fraction of their volume, disengage or absorb 

 the same absolute quantity of heat. 2. That the variations of tem- 

 perature which result, are in the inverse ratio of the specific heat of a 

 constant volume. — Annales de Chimie, tom. xli. p. 1 13. Royal Instit. 

 Journal. 



EXPERIMENTS ON GOLD. BY DR. THOMSON. 



Berzelius and Javal have determined from their experiments that 

 peroxide of gold contains 3 atoms of oxygen. To ascertain the cor- 

 rectness of this statement. Dr. Thomson dissolved 25 grains of gold 

 in nitro-muriatic acid, and to the solution was added one of 104'25 

 grains of crystallized sulphate of iron ; the distilled water was boiled 

 for halfan hour before it was used, and the protosulphate of iron crystals 

 were tin-own into the boiling hot liquid, which was added to the solu- 

 tion of gold as quickly as possible : the gold obtained weighed 24*9 

 grains ; so that the loss was only O'l grain. 



As six times 4-5 grains of protoxide of iron which the 104-25 of 

 protosulphate contained were converted into peroxide, by uniting with 

 3 grains of oxygen. Dr. Thomson considers it as demonstrated that per- 

 oxide of gold is composed of 



1 atom of gold 25 



3 atoms of oxygen 3 



"28 



Dr. Thomson, from the facts stated in his " .Attempt," vol. i. p. 440 ' 

 considered it as extremely probable that muriate of gold is a compound 

 of 2 atoms muriatic acid, and 1 atom peroxide of gold. To determine 

 this by experiment, a solution of gold in nitro-muriatic acid was evapo- 

 rated to dryness, and 242 grains of the metal yielded 42 grains of dry 

 muriate. 



To determine the quantity of muriatic acid, it was necessary first to 

 get rid of the gold ; for nitrate of silver being dropt into the undecom- 

 posed salt, both the gold and muriatic acid precipitate along with the 

 silver j the goldvvas therefore thrown down by copper, the copper by 

 potash, and the excess of potash was neutralized by nitric acid, and 



then 



