42 Mr Johnston on the Cri/stallized 



vented their composition from being investigated so accurately 

 as their interesting nature requires. 



When the powder of algaroth is first thrown down, it forms a 

 beautiful white precipitate ; hut if allowed to stand some lime, 

 or be collected on the filter, it not unfrequeiitly changes in ap- 

 pearance, becomes granular, and assumes a yellowish-grey co- 

 lour. In this state acid is separated from it by washing with 

 water, but its whiteness is not restored. These grains some- 

 times possess a slight degree of lustre ; they are minute crystals. 



If an acid chloride of antimony, prepared by digesting mu- 

 riatic acid in the sulphuret or by any other process, be diluted 

 with 9.0 or 30 times its volume of water, and set aside, the light 

 white powder which at first falls gradually contracts in bulk, and 

 at the end of two or three days has nearly all assumed the cry- 

 stalline form. These crystals are grey, yellowish-grey, or, if the 

 chloride has been prepared from the sulphuret and any sulphu- 

 retted hydrogen is present, of an orange-red colour. They ex- 

 hibit occasionally a high degree of lustre, and, according to the 

 measurement of Professor Miller of Cambridge, are oblique rec- 

 tangular prisms, of which the terminal obtuse solid angles are re- 

 placed by planes. The crystals are generally microscopic, but 

 from their brilliancy the faces are very distinctly observable. 

 Only on two occasions have I observed them form radiated 

 needles, brilliant, almost pure white, and half an inch in length ; 

 the method above described, however, seldom fails to give dis- 

 tinct crystals of a lesser size. 



When these crystals are washed with water, their brilliancy 

 diminishes from the surface undergoing decomposition ; tTiey 

 must therefore be collected and dried on bibulous paper without 

 washing. That these constitute a definite compound there can 

 be no doubt. 



At a temperature considerably above 212° Fahrenheit they 

 lose no weight ; farther heated in a close vessel they decrepi- 

 tate and give oft' white fumes of chloride of antimony; 31.86 

 grains heated to redness in a glass-tube with twice its weight of 

 dry carbonate of soda, and the gas given off made to pass over 

 chloride of calcium, gave only .12 of moisture == 0.38 per cent- 

 This small quantity of moisture was obviously hygrometric 

 either in the soda or the salt. 



