Chemical Science. 153 



observed that, in some circumstances, crystals would form in the 

 solution during cooling, even though the vessel had not been 

 opened or agitated. These crystals, when observed in the solu- 

 tion, are very transparent and of a large size ; they are quadran- 

 gular prisms, with diedral summits. Upon opening the vessel, the 

 surrounding solution crystallizes rapidly, enveloping the first formed 

 set of crystals with others, which, however, are very readily distin- 

 guished from them in consequence of their immediately assuming 

 a white opaque appearance. Upon taking out the crystals, those 

 first formed are found to be much harder than the usual crystals of 

 sulphate of soda, and, when broken, it is found that the opacity is 

 not merely superficial, but that it penetrates them to a considerable 

 depth, and even at times throughout. 



These harder and peculiar crystals are readily obtained by closing 

 up a solution of sulphate of soda, sqfurated at 180°, in a Florence 

 flask, boiling the solution in the flask so as to expel the air before 

 closing it. Upon standing 24 hours, fine groups of crystals are 

 formed. When the flask is opened the solution deposits fresh 

 crystals, but on breaking the flask, the latter may be scraped off 

 by a knife in consequence of the superior hardness of the first 

 set. 



The hard crystals when separated are found to be efllorescent, 

 like those of the usual kind, and they ultimately give off all their 

 water, leaving only dry sulphate of soda. When a given weight 

 was heated in a platina crucible, one half their weight passed off 

 as water, the rest being diy salt. They, consequently, contain 

 eight proportionals of water, or 72 sulphate of soda, and 8 x 9 = 72 

 water. The usual crystals of sulphate of soda contain 10 propor- 

 tionals of water. 



When crystallized sulphate of soda is heated in a flask, a part of 

 it dissolves in the water present, whilst the rest is thrown doAvn in 

 an anhydrous state. Tlie solution at 180° appears to contain one 

 proportional of salt 72, and 18 proportionals of water 162 ; from 

 which, if correct, it would result, that when the crystals are heated 

 to 180° ^ of the salt take all the water, whilst ^ separate in the 

 dry state. — M. F. 



10. Use of Chloride of Calcium^ as a Manure. — M. Chevalier 

 finds that chloride of calcium is useful as a manure, only in the 

 state of very diluted solution, for that, when applied in the solid 

 state to the soil, it destroyed vegetation. It is something, how- 

 ever, to obtain a confirmation of the results mentioned, vol. xvii. 

 p. 362. even though that confirmation be rather general. — Jour, de 

 Pharmacies 1824, p. 611. 



11. Separation of Strontia and Baryta.^- Fluate of silica and ba^ 

 ryta precipitates in crystals almost insoluble. Th^ Jiuate of silica 



