324 Proceedings of the Royal Irish Academy. 



and the odour of nicotine almost disappears ; this solution on evapora- 

 tion will furnish, long prismatic, reddish-brown crystals, the prevailing 

 forms of which are six-sided prisms with truncated ends. These 

 crystals are permanent in the air — at least they appeared to undergo 

 no change by exposure to its influence for a considerable time. This 

 salt is readily soluble in both cold and hot water, and of the former it 

 requires only about 17 times its weight for its solution, and when 

 thus fully saturated with the salt the water acquires a deep reddish- 

 brown colour. It is also soluble in rectified spirit, though rather 

 sparingly so, at the ordinary temperature ; but on the application of 

 heat it dissolves in it readily and in considerable quantity, giving to 

 the solution a dark reddish-brown colour, very similar in its appear- 

 ance to the saturated aqueous solution, and which on cooling yields a 

 considerable proportion of the salt in the crystalline form, and conse- 

 quently spiiit may with advantage be employed in its preparation and 

 purification. It is very slightly soluble in ether, and is almost in- 

 soluble in chloroform. 



A given weight of the salt, which had been dried by means of 

 blotting-paper and by subsequent exposure to the aii', was heated in 

 the water-bath till it ceased to vary in weight, when the crystals 

 acquired a dull appearance from the loss of theii' water of crystalliza- 

 tion ; and the amount of such loss, and the quantity of silver nitro- 

 prusside that the dried salt yielded, agreed very closely with the 

 quantities which should be furnished by a salt having the formula 

 CioHu^s, H2(iS"0)PeCy5 + 2II2O, where one molecule of nicotine was 

 combiued with one of nitroprussic acid, plus two atoms of water of 

 ciystallization. It is therefore by its constitution an acid salt, and its 

 solutions possess a strong acid reaction, and the salt itself has no odour 

 of nicotine. 



I may further observe that in preparing this salt, if sufficient 

 nitroprussic acid has not been added in the first instance to convert 

 the whole of the nicotine into the acid salt, some of the neutral one 

 will remain after the separation of the crystals of the former salt, and 

 on the further addition of the acid a fresh crop of crystals of the acid 

 nitroprusside will be obtained. But a much better way of forming 

 this and other acid nitroprussides of the alkaloids would be to take 

 two equal portions of nitroprussic acid, and, having neutralized one 

 completely with the alkaloid, to add to it the other, when at once the 

 desired end would be obtained. 



Nicotine forms a neutral salt also with nitroprussic acid ; for when 

 that acid is carefully added to an aqueous solution of that base, a neu- 

 tral mixture may be obtained, wliich, on evaporation under a bell- 

 glass in tacuo with sulphuric acid, yields a dark reddish-brown syrupy 

 residue, exhibiting no disposition to crystallize, and evolving a strong- 

 odour of nicotine, and on further drying forms an almost black resi- 

 nous-looking mass. 



This dissolves readily in water, forming a dark-brown neutral 

 solution, which on heating gives off a strong odour of nicotine, and 



