^ 



On the Occurrence of Natro-boro-calcite in Gypsum. 233 



numbers which, notwithstanding the high percentage of water, 

 showed me that I really had to do with natro-boro-calcite. Con- 

 sidering the two ingredients last mentioned as accidental^ I 

 treated a portion of selected mineral with cold water^ washed 

 well with the same, allowed the residue to dry in the air, and 

 analyzed it. It Avas perfectly free of sulphuric acid, and gav^e 

 of the other constituents, 



Experiment. Calculation. 



Soda, - - Y-21 7-82 



Lime, - - - 14*20 14-12 



Boracic acid, - 44-10 4402 



Water, - - 34-49 34-04 



100-00 100-00 



The recurrence of the high percentage of water and the accord- 

 ance of my experimental numbers, both from the purified and 

 the actual mineral, Avith the calculated figures, are ample war- 

 rant, I think, for the following formula which I propose as the 

 true expression for the air-dried natro-boro-calcite, viz: ■ 



Na0 2B03 4-2CaO, SBOa+loHO, 



which differs from that of Ulex, before given, by five additional 

 atoms of water; these, I think it extremely probable, were re- 

 moved by the manipulation with boiling, and possibly by desic- 

 cation at 212°. Indeed I found that when the air-dry mineral 

 was placed in the air-bath at this temperature, it lost, upon sep- 



arate occasions, 



L IT. Mean. 



Water = 8*25 7*58 7-91 per cent. 



which deducted from my total loss, above, leaves 2 G '49 for the 

 amount retained, a number so close to that really obtained by 

 inex~26 — as to leave me little doubt that mine is the true ex- 

 pression. I find also that Hayes* originally gave thirty-five per 

 cent water as the result of his analysis. 



, The minerals just described were fonnd in the closest associa- 

 tion in narrow cavities, perhaps two inches deep, forming a kind 

 of interrupted vein in the body of the solid gypsum-rock, ex- 

 posed by blasting, about thirty feet below the surface, and ex- 

 tending horizontally some few^feet. The more abundant raine- 

 ^^I of the two was the glauber-salt^ so far as I observed person- 

 ally, but the quarry-men told me that at first the other came out 

 ia ''bowlfuls," but they threw it away. I did not obtairf more 

 than a few ounces of the natro-boro-calcite, and perhaps not a 

 pound in all was preserved by those who obtained it on this 



occasion. 



* Liebig und Kopp s Jahresbericht, 1849, p. 780. 



SECOND SERIES, VOL. XXIV, NO. 71.— SEPT., 1857. 



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