20 JOURNAL OF THE 



of water was used to 1 grain of the cyanide a clear deep green was 

 gotten. Witli calcium carbonate, ordinary hydrated calcium sul- 

 phate or barium sulphate, the cyanide when mixed in about equal 

 parts and moistened gave off apparently about the same amount of 

 hydrocyanic acid as when alone, judging from the depth of color in 

 the ferroso-ferric test. AVith the anhydrous sulphate a distinct blue 

 was gotten, showing a decidedly increased decomposition, and in 

 this case the mixture left in the tube had a purplish brown color 

 which was not observed with the others. 



Since other sulphates and other calcium compounds failed to act 

 on the potassium cyanide and no change in the anhydrous sulphate 

 itself could be detected, it seemed probable that its action was due 

 in some way to its \ ower of combining with a portion of the water 

 present to form the hydrated sulphate. When an excess of water 

 3-5 c.c. was added to the mixture of the cyanide and the anhy- 

 drous sulphate the test showed very little, if any, more hydro- 

 cy nic acid to be given off than when the hydrated sulphate or the 

 cyanide alone was used and no discoloration was produced. When 

 barely moistened thi? evolution of hydrocyanic acid was considera- 

 ble. If porous, partially dehydrated calcium chloride was added 

 to the cyanide in the place of the sulphate the amount of acid 

 evolved was still greater and .the color of the mixture almost black. 

 Anhydrous sodium carbonate had tliesame effect, though in a lesser 

 degree. Again, when the cyanide and the plaster had both been 

 carefully dried, the air was drawn over them for four days and no* 

 ' ydrocyanic test could be gotten in the final tube of potassium hy- 

 droxide. 



The mixture of potassium cyanide and anhydrous calcium sulphate 

 left after two or three days of aspirating was examined and to con- 

 tain potassium h droxide. The reaction then is probably 



KCN + H.O = HCN -f- KO'H. 



It has been shown by Karsted (Poggendorff \s Annalan, 115, 348) 

 and Storer (Amer. Chem. Journal v. 69) that where air alone comes 

 in contact with corks and organic connectors carbon dioxide is 

 formed. This would probably account for decomposition when 

 potassium cyanide and water alone were used, but the greatly in- 

 creased depth of test when plaster of paris is added shows a decided 

 action on the part of that body. 



Chemi-al Laboratory, U. N. C, Nov., 1883. 



