( 199 ) 



So we can derive from the table that /^i contains about 1,3 mol. % 

 H^O and L, 3,4 mol. "/„ H^S at the quadruple point. Soit appears 

 really that non-miscibility extends almost over the full width of the 

 figures of concentration. 



2. In the preceding communication uncertainty continued to prevail 

 about the constitution of the hydrate. The first analysis of the hvdrate 

 found by Wöhler in 1840 was made by de Forckand. In reference 

 to these analyses, which (irst led to the formula II.,S \b (iq ^), after- 

 wards to H..S 12 aq -), DK FoRCKAND i-emarks that it is diiTicult to 

 obtain this compound in dry state; generally in the formation of 

 the compound a quantity of water remains excluded from the action 

 of the gas owing to its being enveloped by a layer of solid substance. 

 To this difliculty, which presents itself in a perfectly analogous way 

 for other gas-hydrates, it is owing that the most divergent formulae 

 have been proposed for the concentration of the hydrates, which 

 possess the smaller ratio of water as the investigations were repeated 

 with greater care. Thus in an analysis carried out latei- on by dv. 

 FoKCRAND and Villard the concentration H,^S 7 aq appeared to be 

 the most probable one ^), but of this analysis the two investigators 

 state that also in this case the ratio of water is probably still too 

 high. Villard") comes to this conclusion on account of the great 

 analogy between this hydrate and the numerous other hydrates 

 examined by him, for which his extensive investigation has made 

 the general formula M.QHJJ probable. Besides in virtue of this 

 analogy Villard thinks he han to ascribe the analogous formula 

 H^S . Q H,0 to the hydrate of H._S, also on account of the possil)ility 

 of seeding a mixture of ^^0 and H.^0 with the hydrate of H^S, 

 so that X.,0 .^ HM is deposited. Villard has, however, not made 

 any direct determinations to prove this constitution. 



Dk Forcrand arrives at the same conclusion by another way. 

 From some regularities found empirically between caloric quantities 

 and the temperature, in which the line SL^G reaches the pressure 

 of one atmosphere, de Forcrand finds a means to calculate the 

 concentration of the hydrates. This calculation, which I shall not 

 discuss any further iiere, has yielded the value //^-S' . 5,69 ^/Y for the 

 hydrate of hydrogen sulphide';, which led de Forcrand to conclude 

 to the formula H^S.^aq. 



1) De Fohukand. C. r. 94 '.JG? (1882). 

 -) De Forcrand. Ann. chim. phys. (5). 28. 5 (1883). 

 3) De Forcrand and Villard. C. r. 106. 1402 (1888). 

 ^) Villard. Ann. chim. phys. (7) 11 -I'S',) (1807). 

 ^) De Forcrand. C. r. 135. 959 (1902). 



