and dilute Stdphuric Acid, 99 



the yellow salt collected, washed, and dried at 220°, weighed in 



Experiment No. 1, 88*1 grs. ; No. 2, 88*0 grs. ; No. 3, 87*1 grs. 



The calculated number is 87*16. The salt is very liable to 

 assume a delicate green tint unless the air be very carefully 

 excluded from the vessel, and hence its true colour cannot be 

 seen, unless the flask, previously to adding the acid, be filled 

 with carbonic acid gas ; the green tint always goes off on dry- 

 ing it at about ^00° F. 



{b.) The colourless solution which passed the filter, leaving 

 the yellow salt on it, and which contained the bisulphate of 

 potassa, required, to render it neutral, of crystallized bicarbo- 

 nate of potassa, (I used this as being the most definite and 

 manageable salt we have,) in 



Experiment No. 1, 152*1 ; No. 2, 151*0; No. 3, 150*6 grs. 



The calculated quantity isl4(K + 2C+l Aq) 150*58 grs., 

 showing that 3 proportions of sulphuric acid had taken up only 

 1^ potassa. After neutralizing the liquid with bicarbonate of 

 potassa, it was in two cases evaporated to dryness, and the neu- 

 tral sulphate weighed, which confirmed in both cases the above 

 results, and proved that no other salt was in the solution : also 

 in one case, the sulphuric acid was precipitated by nitrate of 

 barytes, which proved that all the sulphuric acid was in the 

 solution. 



{c.) The hydrocyanic acid given off was estimated by taking 

 106*3 grs. of the ferrocyanuret of potassium in 2 fluid ounces 

 of water, + (300 grains of dilute sulphuric acid of specific 

 gravity 1*179) = 60 grains of real acid, and by means of a 

 tube and cork conducting the vapour into a large receiver, 

 containing a dilute solution of nitrate of silver: the cyanide 

 collected and weighed, gave in 



Exp. No. 1, 103 grs. ; No. 2, 102*3 grs.; No. 3, 101*4 gr. 



The calculated number is 100*8 grains. Most likely in ex- 

 periment No. 1. the matter was not perfectly dried; but the 

 three come sufficiently near to leave no doubt of the theoretical 

 quantity. 



(4.) Hence I conceive that the exposition of the reaction 

 given at the commencement of this paper is fully proved. I 

 am well aware that in the 46th volume of the Annales de 

 Chimie et de Physique, p. 77, M. Gay Lussac states that a 

 white salt is produced during this reaction. I have operated 

 with distilled sulphuric acid, conducted the process in a nar- 

 row-necked flask, into which a stream of carbonic acid passed 

 during the whole of the boiling, and it was always of a light 

 lemon colour : in ordinary cases, when this extreme care was 



2 



