1824.] Chemical Examination of the Baryto-Calcite. 115 



Chemical Examination of the Baryto-Calcite. By J. G. Chil- 

 dren, FRS. &c. 



With the blowpipe this mineral exhibits the following cha- 

 racters. 



In the forceps, in the oxidating flame, it neither fuses nor 

 decrepitates ; its surface becomes green, and the point of the 

 flame, beyond the assay, assumes a light greenish-yellow colour. 

 In the reducing flame the superficial green colour disappears. 

 The assay, after being ignited, browns moistened turmeric paper. 



Heated to redness, in a glass tube, it merely gives off a little 

 moisture. 



By heat the assay becomes strongly phosphorescent, shining 

 with a pale-yellow light, very similar to that of the common 

 glow-worm. 



With soda, on the platina wire, in the oxidating flame, it gives 

 a bluish-green opaque mass. In the reducing flame the green 

 colour is discharged. 



With borax, in the oxidating flame, dissolves readily into a 

 perfectly diaphanous globule of a beautiful light amethystine 

 colour. The globule retains its transparency in the reducing 

 flame, but entirely loses its colour. 



With salt of phosphorus, dissolves very readily ; the globule is 

 perfectly transparent, and in the oxidating flame yellow while 

 hot ; when cold, colourless. In the reducing flame the globule 

 is colourless, and, while hot, transparent ; when cold, its trans- 

 parency is slightly disturbed. 



Analysis. 



To ascertain the proportions of its elements, I dissolved the 

 mineral in muriatic acid, diluted the solution very largely with 

 distilled water, and precipitated the barytes by sulphate of 

 ammonia ; boiled the precipitate to take up any sulphate of lime 

 that might have been thrown down, filtered, and washed the 

 precipitate, till the washings ceased to give any cloud with oxa- 

 late of ammonia, adding the washings to the solution from which 

 the sulphate of barytes had been separated. The solution, being 

 first reduced by evaporation, was then boiled with a solution of 

 carbonate of potash, which threw down the lime in the state in 

 which it originally existed in the mineral. Treated in this 

 manner, 'JO grs. gave 



Grains. 



Sulphate of barytes 15*55 grs. = carbonate of barytes 13-18 

 Carbonate of lime 6*72 



iy-yo 



A minute portion, not exceeding one or two-tenths of a grain, 



i 2 



