228 Prof. Davy on the Action of Nitric and 



Find log it to twenty places. 



3-14159 26 535 89793 23846 264 ... it 

 3-14159 25 



1-535 89793 23846 264 n ...log... 0-18636 23557 50839 



5615. . 3-74934 97605 97476 58947 ... log - 5*88843 45507 03060 



5595.. 3-74780 00908 64368 54759 ...A.C. 6-25219 99091 35631 



[212 32288] 2 32699 68155 89530 



iM^ -106 16144 



x 



212 32288 42729 ...log 2-32699 68049 73386 



7*49714 98726 94133 86435 



Restoring the proper index, we have 0*49714, &c. 



XXVIII. On the Action of Nitric and Nitrous Acids on the Sul- 

 phocyanides. By Edmund William Davy, A.B., M.B., 

 M.R.I.A., Professor of Agricultural Chemistry to the Royal 

 Dublin Society, fyc* 



SOME time since, having had occasion to test a sample of 

 carbonate of potash (which I believed to be very pure), to 

 ascertain if it was perfectly free from iron, and suitable for the 

 purpose required, I was surprised, on dissolving a little of it in 

 water and supersaturating the solution with some carefully 

 purified nitric acid, to find that the mixture, on the addition of a 

 few drops of a solution of sulphocyanide of potassium, became of 

 a reddish colour, indicating apparently the existence of a small 

 quantity of iron in the mixture. Conceiving that the coloration 

 observed was caused by the presence of that metal, I proceeded to 

 ascertain whether it existed in the acid or in the carbonate. A 

 few experiments showed me that the effect was due to the acid ; 

 for I found, on testing a diluted portion of it with sulphocyanide 

 of potassium, that it soon acquired the same reddish tint; 

 whereas some of the carbonate of potash, after supersaturation 

 with pure hydrochloric acid, did not acquire the reddish tinge 

 on the addition of the sulphocyanide, or give the slightest indi- 

 cation of iron when tested with either the ferrocyanide or ferrid- 

 cyanide of potassium, clearly proving that the effect observed 

 was alone attributable to the acid. This I thought was rather 

 singular, as the nitric acid I employed was very carefully pre- 

 pared by myself, and I believed that it was chemically pure. A 

 considerable portion, however, of this acid being evaporated 



* Communicated by the Author. 



