APPENDIX B. XVI] 



can be obtained from which the first crystals of tartaric acid 

 are procurable. Ammonia, the other constituent of the 

 neutral tartrate, being a product of the destructive distillation 

 of coal tar — and itself exercising such a destructive influence 

 upon organic matter when existing in the form of strong 

 liquor ammonice — would not seem to be a very promising 

 nidus for living ' germs.' The neutral tartrate of ammonia 

 is, however, prepared by mixing a solution of tartaric acid, 

 procured as above mentioned, with an adequate quantity of 

 liquor ammoniae, and then evaporating the mixture at a 

 gentle heat. Thus prepared, the crystals contain a notable 

 quantity of water of crystallization. 



In the stock of crystals procured from Messrs. Hopkin 

 and Williams^ which had been made about six months pre- 

 viously, some were well formed, and almost perfectly trans- 

 parent, whilst others were less regular in shape, and pre- 

 sented an opaque appearance with more or less of striation 

 within. When a crystal of moderate size was taken, about 

 ^'' in diameter, or a portion of a larger one, and placed in 

 a large watch-glass with some distilled water, it was frequently 

 found that at first a certain number of opaque-white 

 scales, having a granular aspect under a high magnifying 

 power, dropped from the surface of the crystal to the bottom 

 of the watch-glass. This material, which seemed to have been 

 produced by some superficial alteration (efflorescence) of the 

 substance of the salt, dissolved with much more difficulty 

 than the unaltered matter of the crystal. It remained for a 

 long time at the bottom of the glass, and only very slowly 

 disappeared. As the substance of the crystal thus dis- 

 solved away, a number of large and small gaseous bubbles 

 gradually escaped from it. When the crystal was examined 



at ordinary temperatures, has been found to be peculiarly destructive to 

 all living things. 



^ Of New Cavendish Street. 



VOL. II. 



