200 Professor Gmelin's Analysis of' a 



The specific gravity of this Mica would accordingly be = 2.8427, 

 at + 9a° R. Eight hours after, during which time the bits 

 were lying in water, the specific gravity was found = 2.8603, 

 the temperature of the water being + 9^° R- After three days, 

 when they had always been lying in water, the specific gravity 

 was = 2.8929, at -j- 10^° R. Their weight in water no longer 

 changed in a sensible manner. These variations in the speci- 

 fic gravity evidently depend on air interposed between the la- 

 mina? of this Mica, which is by degrees displaced by the wa- 

 ter when it is lying in this fluid, whereby the specific gravity 

 is increased. 



B. Relations before the Blow-Pipe. — This Mica fuses so 

 readily, that very thin lamina?, when held in the flame, without 

 blowing upon it, melt to a globule. In the flame which is as 

 usual blown at, even thick lamina? quickly melt (swelling 

 up, and imparting to the flame a beautiful purple colour) to 

 a white glass, full of blisters, which, at the moment when it is 

 removed from the flame, is transparent, but soon becomes opal- 

 escent. In the matrass, it gives off" water which tinges Brazil 

 wood paper yellow, and contains, of course, fluoric acid ; the 

 glass is somewhat corroded. Borax dissolves it in large quan- 

 tity to a clear glass, which has an amethyst colour in the oxy- 

 dating flame, but is discoloured by the interior flame. Salt of 

 phosphorus dissolves it, leaving a skeleton of silica ; the glass 

 opalesces a little after full cooling, and then also the manga- 

 nese reaction is perceived, which becomes much more distinct 

 by means of nitre. Soda dissolves it with effervescence to a 

 clear glass, having an amethyst colour from manganese. Upon 

 a platinum lamina, the green reaction of manganese is very 

 marked. Moistened by nitrate of cobalt, it becomes blue, 

 when melted. 



C. Analysis. — 1. Determination of the Bases. — 1.402 

 grammes were cleft thinly by a knife, then cut into small 

 quadrangular pieces by scissars, mixed with six times their 

 weight of carbonate of barytes, and ignited in a platinum cru- 

 cible. During one hour, the crucible had been kept mode- 

 rately red-hot, when, during half an hour, the fire was in- 

 creased to whiteness. The ignited mass appeared half melted, 

 and of a green colour ; the form of the micaceous lamina?, which 

 now showed a deep green colour, was still discernible in it. 



