88 Mr. J. D. Smith on the Hydrates ofBarytes and Strontia. 



periments would indicate SI'? parts or nearly 9\ eqs. of 

 water combined with 76 parts or I eq. of barytes ; this error 

 is doubtless owing to your not having obtained the crystals 

 quite dry, and not making allowance for the interposed water, 

 which, in that case, they would have contained. 



When crystals of barytes are heated to 212°, they fuse in 

 their water of crystallization, and by continuing the heat until 

 no more vapour is expelled, a porous and friable mass re- 

 mains. 20 grs, of this residue being heated with hot water 

 left 3'03 grs. of insoluble (carb. of barytes), and the solution 

 precipitated by dilute sulphuric acid, gave after ignition 20'64' 

 grs. of sulphate = 13'52 grs. of barytes. This experiment 

 repeated on the same quantity gave 1*28 grs. of insoluble 

 carbonate and 22"97 grs. of sulphate — 15 grs. of barytes. 

 In the first experiment 20 — 3-03 = lG-97 — 13*52 of 

 barytes leaves 3-4'5 for water; and in the second, 20 — 1*28 

 = 18"72 — 15' barytes leaves for water 3'72, the mean of 

 which, !4"26 of barytes and 3'58 of water, is equivalent to 

 76 parts, or 1 eq. of barytes combined vvith 19 parts or a 

 little more than 2 eqs. of water. This is the compound cor- 

 responding to the fifdi hydrate of Dalton. 



By exposing the crystallized hydrate to a red heat in a 

 covered platinum crucible, applying the heat cautiously and 

 gradually, it at first enters into the watery fusion, during 

 which care must be taken to prevent it from boiling over, after 

 which it fuses quietly down, leaving a light brown-coloured 

 mass possessing a crystalline structure. 



20 grs. of the crystallized hydrate heated to redness in a 

 platinum crucible left 10'87 grs. —20 = 9*13 grs. of water 

 expelled. 20 : 91*3 : : 157 the eq. of cryst. bai-ytes : : 71*6, or 

 almost exactly 8 eqs. of water, leaving 1 eq. of water in 

 combination with 1 eq. of barytes. 28"52 grs. of the crystals 

 left after ignition 15'47 = 13*05 grs. of water driven off, or 

 71 "83 = 8 eqs. of water from 157, or 1 eq. of the crystallized 

 hydrate. Thus the residual mass obtained by heating the cry- 

 stallized barytes to redness is evidently a compouncl of 1 eq> 

 of barytes + 1 eq. of water, and there exist three distinct 

 hydrates of barytes, viz. 



The 3rd, deposited from solution in water ; the 2nd, obtained 

 by heating the crystals in a water bath; and the 1st, by heat- 

 ing either of the preceding hydrates to redness, without access 

 of air. 



equivalent numbers-. 



