114 On Salt Solutions and Attached Water. 



of no common interest, Ten of these concretions, which 

 are remarkably uniform in size, weighed 0*5024 gram ; the 

 loss on heating to 200° C. in an air-current was 0*1432 gram, 

 showing 28*504 per cent, of water. This points to the formula 

 CuSCXt + 3-5 H 2 O ; and, as I hope to show in my next com- 

 munication, the subdivision of the water molecule in hydrated 

 sulphate of copper, or rather the multiplication of the whole 

 formula of that salt, does not admit of doubt, Here again we 

 have evidence of the continuity of composition according to 

 physical circumstances (compare § 142). But what a com- 

 plete chain of difference of diffusive potential is here indicated, 

 stretching from the first nucleus throughout the jelly ! and 

 how it suggests the diffusion and accretion of the matter of a 

 crystalline mineral through a colloid and, perhaps, mechani- 

 cally rigid mineral matrix I 



To return to the green colour of the copper jelly. Gelatine 

 is so complex a body, that although the formation of the blue 

 crystals of the sulphate shows that there has been no general 

 chemical change, yet there is no evidence of its entire absence. 

 Glycerine was therefore next employed as a medium for the 

 solution of various coloured salts. 



§ 191. Anhydrous sulphate of copper dissolves so abun- 

 dantly in glycerine that the solution may be almost solid when 

 cold. There is no sign of crystallization ; but the solution at 

 all strengths is a bright emerald-green. 



§ 192. Crystals of permanganate of potassium, when heated 

 with glycerine, oxidize it with the escape of gas ; but if cold 

 glycerine is added to a cold saturated aqueous solution of the 

 permanganate, a liquid is obtained, without evidence of che- 

 mical change, which has been pronounced to be brownish 

 yellow, amber, or, perhaps more accurately, " raw-sienna ; " In 

 view of the possible chemical change Avhich may be incipient 

 here, it is perhaps better to put this result on one side. 



§ 193. Chloride of cobalt, which in water gives the well- 

 known pink hues according to its strength, gives with glyce- 

 rine a beautiful carmine ; this, when heated, is greatly enriched 

 in its blue. When cooled in a carbonic acid cryogen, it acquires 

 a yellowish tint. 



§ 194. Chromium potash alum, which in water gives the pale 

 indigo of dilute ink, gives with glycerine an emerald-green. 



Whatever be the degree of intimacy of association between 

 the glycerine and the salt, it appears, then, that this association 



some Points in the Natural History of Uric Acid and Urates" (St. Thomas's 

 Hospital Reports, 1875) ; " Urinary Crystals and^Calculi," &c. (Medico- 

 Chirurgical Transactions, vol. lviii. March 9, 1875). 



