C. H. Palmer — EemarhaUe Case of Hydration. 47 



These samples began to change color at the temperature of 

 the sand bath and at red heat turned black. Treatment of this 

 black residue with acids, and even prolonged and repeated 

 fusion with potassium bisulphate, failed to bring all the copper 

 in solution. Sodium cai'bonate fusion was not tried. 



The most remarkable feature of the whole affair is that a 

 mineral or chemical compound should occur in nature with such 

 a large amount of water so loosely attached to its molecular 

 structure. Chrjsocolla not being a crystalline mineral, the loss 

 of water of crystallization is not indicated by the loss of crys- 

 talline form, and neither is there a change of color upon the 

 loss of the very portion that would ordinarily be regarded as 

 water of crystallization. Diligent search of the literature of 

 hydrous minerals in general, and chrysocolla in particular, 

 accessible to the writer, failed to indicate that any such unusual 

 behavior has been previously noticed. Heretofore, a loss of 2 

 or 3 per cent over sulphuric acid has been regarded as probably 

 the limit to be expected, even in special cases, from the minerals 

 containing water most loosely combined, as in the zeolites and 

 others. 



It seems almost superfluous to mention, in this connection, 

 the importance of including in the results the so-called hygro- 

 scopic moisture in the analysis of minerals. Indeed, upon com- 

 paring the results given above ( only the last two analyses are 

 referred to for comparison, as the flrst is too obviously a mixture) 

 with the published analyses of chrysocolla given in the table 

 l)elow ( from Eammelberg's " Mineralchemie," 1860, page 551 ), 

 one is inclined to suspect that possibly considerable "hygro- 

 scopic" water was overlooked in some of the latter, or else 

 there is something inherently different in the two classes. It 

 will be noticed that while the amounts of silica are similar, the 

 cupric oxide in No. 2 and ^N'o. 3 is about one-fourth less 

 and the amount of water is about one-half as much more than 

 the other analyses show. The loss of No. 2 and No. 3 over sul- 

 phuric acid closely approximates two-thirds of the total water 

 present. 



3 



1 2 ""« & , 4 5 



SiO, 37-25 40-00 35-00 36-54 35*14 32-55 



CuO 45-17 42-60 39-90 40-00 43 07 42-32 



Fc^Og- 1-40 3-00 1-00 1-09* 1-63 



CaO-. - -- 1-76 



M^rO --- 1-06 



H^^O 17-00 16-00 21-00 20-20 20-36 20-68 



Gangue .. 1-10 2-10 



99-42 100-00 100-00 99-84 99-66 lOO'OO 



*Witli AI2O3, CaO, K2O. 



