lio 



Mr Johnston on the atomic constitution 



The fourth column indicating the weight of cyanogen com^ 

 bined with 25 grains or one atom of mercury according to these 

 results, is obtained for No. 1, by the following ratio : — 

 1.995 inches cyanogen = 1.097 grains. 

 ;. 3.903 : 1.097 : : 25 : 6.7, and so on for the rest. 



Now, 6.5 being the weight of two atoms cyanogen, No. 1 

 errs in excess ; the three others are a little deficient. The 

 errors, however, are very small ; for even No. 3, which is the 

 most incorrect of those deficient, would have given 6.5 for the 

 atomic proportion had the carbonic acid collected been only 

 one-twentieth of an inch greater. This error may be due either 

 to measurement or to a minute portion of the cyanide remain- 

 ing undecomposed. No. 1 is so much ( half a cubic inch) in 

 excess, that I fear there must have been some cause of error 

 which I could not discover. 



2. Five grains of cyanide heated in like manner with 50 

 peroxide of mercury till gas ceased to come over, gave in three 

 experiments 



Carbonic acid. Azote. 

 No. 1, 3.84 inches 1.865 



2, 3.882 1.8 



3, 3.83 1.926 



Cyanogen. Atomic proportion. 

 1.92 6.69 



1.941 6.7 



1.915 6.65 



Mean atomic proportion, 6.68 



These results agree in being all in excess. The quantity of 

 azote is also greater than by the peroxide of copper, and in 

 No. S is almost exactly half the volume of the carbonic acid. 



3. When the cyanides, the sulpho-cyanides, the ferro-cyan- 

 ides, or the new salts called the red * ferro-cyanides, are mixed 



• The Cyan Eisen Kaliura (Rothes) of Gmelin ; the Cayanure Rouge de 

 Potassium et de Fer of Robiquet, is the only one of these hitherto employ- 

 ed for chemical purposes. Robiquet disputes with Gmelin the right of 

 discovery, because he knew nothing of Gmelin's published experiments till 

 he had made his own. On the same ground I might advance a similar claim, 

 as I obtained the potash salt three years ago in beautiful crystals, and was 

 indebted to Dr Thomson for directing me to Gmelin's paper. But my 

 mode of forming the salts leading me to infer the presence of chlorine, I 



