314 Proceedings of the Royal Irish Academy. 



at first amorphous, or in tlie form of minute oil-like globules, which 

 latter, on subsiding or on agitation, adhere to the sides and bottom of 

 the vessel containing the mixture, forming a sticky resinous-looking 

 deposit, or the particles agglutinate together into little lumps or masses 

 of a similar character. But these deposits, on standing for a variable 

 period, assume for the most part a more or less crystalline condition. 

 In some cases, however, as for example in that of veratiine and cin- 

 chonicline, there appeared to be no disposition on the part of the salts to 

 acquire a crystalline form, even after the lapse of a considerable time. 



In the preparation of those nitroprussides of the alkaloids, which, 

 owing to their slight solubility in water, may be obtained by precipi- 

 tation, as already stated, using any of theii' soluble salts, still it will 

 be found better in most cases to employ the alkaloid in the form of 

 the sulphate ; for this reason, that in the after-washing of the precipi- 

 tated nitroprusside, to free it from the sodium salts with, which it is 

 associated, where the sulphate is used we can easily ascertain whether 

 this has or has not been completely effected, by testing for sulphuric 

 acid with a barium salt, a small quantity of the filtrate (the water 

 used in washing the precipitate); and when such fails to produce any 

 turbidity, it may be considered to be sufficiently washed and all the 

 sodium sulphate with which it was mixed removed. But shoiild the 

 acetate, nitrate, or chloride have been employed, it will not be so easy to 

 ascertain this point. As regards the employment of a chloride of the 

 alkaloid in this case, I may observe that, as more or less of the nitro- 

 prusside of the alkaloid is always dissolved during the washing process, 

 its presence in the filtrate interferes with the use of a silver salt for 

 the detection of the alkaline chloride formed along with the nitro- 

 prusside when the chloride of the alkaloid was the salt employed. 



Some of the alkaloids, as those of moi'phine and nicotine, as they 

 form very soluble salts with nitroprussic acid, their nitroprussides 

 cannot be obtained by precipitation, as in the case of the former alka- 

 loids ; but they can be easily made, either by directly dissolving the 

 alkaloids in nitroprussic acid, or by treating solutions of their chlorides 

 with silver nitroprusside, or their sulphates with a solution of barium 

 nitroprusside, when, in the first case, the insoluble silver chloride, and 

 in the second that of barium sulphate, is formed, either of which can 

 be easily separated by filtration from the soluble alkaloid nitroprusside 

 produced ; which on subsequent evaporation, if the salt is erystallisable, 

 can be obtained in a crystalline form. But as it is difficult to know 

 the exact quantity of the barium salt which should be added to de- 

 compose completely the sulphate of the alkaloid, the use of the silver 

 nitroprusside, with the alkaloid in the fonn of a chloride, is to be pre- 

 ferred ; as owing to its being an insoluble salt, if it be added in excess 

 it remains without contaminating the nitroprusside of the alkaloid : 

 indeed it is better, as a general rule, that it should be so added, to 

 ensure the complete decomposition of the chloride of the alkaloid, and 

 such excess will be entii'ely removed during the filtering of the mix- 

 ture, to separate the insoluble silver chloride formed in the process. 



