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Bertliier, Richter, Bticholz, and other equallydistinguished chemists used the barytes pre-pared from the nitrat of barytes by a strongheat, which destroys the acid and leaves thebarytes pure. In the first instance the baryteswas more easily fusible than the other, andwhen cold had the appearance of a semi-trans-parent glass. The barytes from the nitrat onthe other hand required a much greater heatfor its fusion, and in melting absorbed a littlecarbonic acid. By adding a little water tothis barytes it became in every respect like theother. The barytes from the watery solutionof this earth, was also strongly heated withiron filings in a porcelain retort, and gave outa large quantity of hydrogen. From thesefacts the author shews that the barytes fromthe aqueous solution is a llydral of Barytes ,containing about 10 per cent, of water, and thepurer form of barytes is that which arises fromthe calcination of the nitrat.

This discovery led the author to suspect thatpotash might retain water when heated per se,and give it up when it enters into saline com-binations. The principal experiment is thefollowing : Some potash was melted in a silvercrucible whose weight was known, and kept infusion till it exhaled white vapours, when thecover was lifted off. The crucible with its«ontents was weighed when cool, and 15.73grammes of fused alkali were found to be con-tained in it. This was dissolved in muriaticacid, and the whole solution with the washingswas carefully evaporated and ignited in a pla-tina crucible, till the muriat of potash was inperfect fusion. When cold, the muriat ofpotash weighed 20.335 grammes, and producedwith nitrat of silver 38.5S6 gr. of well driedluna cornea, which (reckoning 17.5 per cent,of muriatic acid in luna cornea) indicated6.752 gr. of acid. Consequently the 20.335of fused muriat of potash consisted of 6.752of muriatic acid and 13.583 of potash; but15.73 of fused caustic potash was employed,and hence the difference between 15.73 and13.583 (2.147) is the quantity of water con-tained in the fused caustic potash, which givesthe proportion of 13.64 of water in 100. offused potash.

The existence of a large quantity of water ofcomposition in fused potash is also shewn byheating the alkali strongly with iron filings ina porcelain retort, by which a prodigious quan-tity of hydrogen gas is given out.

It appears however that though fused potash

c Recherchcs Physic

gives up a large quantity of its water of com-position when neutralized by an acid, yetsome water is still retained, at least by one orother of the component parts of the compound,for most saline bodies will give hydrogen whenheated strongly with iron filings.

Messrs. Gay-Lussac and Thenard,® havealso made several experiments to determine thequantity of water contained in fused causticalkali prepared with alcohol. A portion offused potash was carefully weighed in a closedvessel, it was then taken out, put upon a dishof platina, and introduced into a large glassglobe nearly full of a measured quantity ofcarbonic acid, standing over mercury, so thatthe alkali did not touch any portion of the glass.I he alkali was then heated very gradually,when it became white on its surface, softened,rapidly absorbed the carbonic acid gas, and inso doing such a quantity of water was disen-gaged as to trickle down the sides of the glassglobe. The heat was very gradually raised toa cherry red. The water was then absorbedby blotting paper, and the remaining ,borne-acid gas measured, and the carbonat of potashweighed.

A similar experiment was performed on fusedsoda.

The results of these were, that 100'parts offused potash in combining with carbonic acid,give up 13.596 parts of water; and 100 partsof fused soda give up 22.166.

The next experiment was to combine thealkali with silex by fusion, forming a glass.A given weight of the fused alkali and ignited,silex were put into a silver crucible, and somewater added to promote an entire mixture ofthe ingredients, M^ficli was then slowly driedand ignited to redness for an hour. The resultwas a perfect glass, which was weighed. Fromthis experiment, 100. parts of fused potashwere found to contain 18.45 of water of com-position, and 100. parts of fused' soda contain26.15 of water.

The third experiment was the following:A certain weight of fused potash and of fusedsoda were saturated with sulphuric acid andthe quantity noted. On the other hand knownquantities of potassium and sodium were ex-posed to a moist air in long narrow vessels,till they were converted into their respectivealkalies, which were then saturated with thesame sulphuric acid as that employed before.Hence supposing the alkali produced from the*potassium and sodium to be pure, and freei-Chimiques, tom , 2..