tS2d,] On fie Reaction of Sulpfutte of 'Magnesia, ^c. 403 



salt is dissolved in water and crystallized, it yields common 

 crystals of glauber salt to the very last drop. 



These experiments leave no doubt that the salt is really an 

 anhydrous sulphate of soda, as it had been thought to be by 

 Mr. W. Wilson ; so that the only difference between it and 

 glauber salt is the absence of all water. 



Thus it appears that sulphuric acid and soda are capable of 

 combining and crystallizing without water as well as sulphuric 

 acid and potash. Three distinct species of sulphate of soda are 

 now known to exist. 



1. Anhydrous sulphate, crystallizing in a boiling solution, 

 and crystallizing in octahedrons with rhomboidal bases. 



2. Common sulphate of soda, containing 10 atoms water, 

 crystallizing in a cold solution, and forming crystals which have 

 the shape of doul)ly oblique four-sided prisms. 



3. Sulphate of soda crystallizing m a supersaturated solution 

 of sulphate of soda made in a high temperature, and set aside 

 for some days in a well-corked phial. The crystals are opaque, 

 \vhite, four-sided prisms, and contain eight atoms of water 

 instead of ten. The first account of this variety was published 

 by Mr. Faraday. There is a description and analysis of it made 

 some years ago by myself in one of my common-place-books. 

 I had forgot the circumstance, till it was brought to my recol- 

 lection by Mr. Faraday's paper, which I saw for the first time 

 about two months ago in a German journal. 



Article IL 



On the Reaction of Sulphate of Magnesia and Bicarbonate of 

 Soda. By M. Planche.=^ 



It is known that the bicarbonate of soda and the sulphate of 

 magnesia, in a state of aqueous solution, exercise no reciprocal 

 action in the cold, and that it is only when a certain quantity of 

 carbonic acid has been disengaged by heat, or, in other words, 

 >vhen the alkaline bicarbonate has passed into the state of sub- 

 carbonate, that the sulphuric acid prevails over the soda, and 

 leaves the magnesia to the carbonic acid. But I have nowhere 

 seen it mentioned that the two salts mixed together, in a dry 

 state, and in the form of powder, react upon each other. This 

 must at least be the case with regard to their immediate and 

 instantaneous mixture, since in this state they dissolve in water 

 without affecting its transpareircy, and consequently without any 

 decomposition taking place, or at least any apparent decompo- 



* From the Joutnal de Phatmacie. 

 2d2 



