OBSERVATIONS IN CHEMISTRY AND MINERALOGY. 419 

 I. 0.5 gram of blue vitriol was dissolved in 25 c.c. of water. This gives 



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0.127 gram of copper in the 25 c.c. of liquid, or 0.5 per cent. The liquid was 

 saturated with sulfur dioxyd gas at 20° C. about, and then sealed in a suitabh 

 glass-tube. Tube was then kept at 110°-120° C. in an air bath over night 

 Liquid looks colorless and a fine crop of copper crystals had formed, cubo- 

 octahedrons and dodecahedrons. Upon opening the tube there was still a stron 

 smell of sulfur dioxyd. After filtering the solution shows blue color and was 

 precipitated by hydrogen sulfid. Result: 74 per cent, of copper had fall i out 

 26 per cent, remained dissolved, notwithstanding the excess of sulfur dioxyd still 



remaining. 



II. Repeat with all conditions alike except the temperature. This was kept 



at 135° C. over night. Solution had become colorless, with a crop of fin< pper 

 crystals. The ratio of precipitated copper to total copper was 93 : 100. 



III. A saturated solution of blue vitriol was saturated with sulfur dioxyd and 

 placed in air-bath. It exploded. 



IV. Same saturated solution saturated with sulfur dioxyd was scaled up in 

 tube and placed in air-bath at 2 P. M. When - <amined at 3 1 M. the ther- 

 mometer showed 95° C. ; a large crop of dark, prismatic crystals had formed, re- 

 sembling spikes, and only a small quantity of metallic copper. In bright day- 

 light the crystals are deeply blood-red and reminded me of chalotrichite or hair- 

 ruby copper. A closer examination, however, did not confirm 1 he first imj >ression 

 The development of the faces at the pole did not agree with the isometric sym- 

 metry. It then occurred to me that the substance might be cuprosxdfite Cu 2 

 (S0 3 ).H 2 mentioned by several authors. 



Analysis. — In tube gives water, turns pale blue and leaves a black residue 

 A 1/100 normal solution of potassium permanganate acidified with nitric acid 

 and brought into contact with the crystals becomes at once decolorized. This 

 is good proof of sulfite. The salt would break up at the proper tern] Tature 

 into 2CuO + S0 2 -f- H 2 0. We should get from 224 parts of the salt 158 pans 

 of CuO. Actually I obtained from 0.01 529 gram a residue of 0.094 gram (weights 

 are accurate to fifth decimal, because weighed on a very delicate button balance). 



224 : 158 = 0.0153 : x; x = 0.0099. 



That is to say the analysis gives 0.0094 when the theory requires 0.0099. The 

 microscope reveals small, granular, pale-bluish crystals sitting upon the blood- 

 red crystals. They cannot be removed with water and are therefore not copper 

 sulfate as I first thought. They are probably Cu(SO s ).wH 2 a cuprisulfite? 

 But their presence explains the discrepancy between 94 and 99 in the result of 

 the analysis. The form of the red crystals is undoubtedly morwclinic. Ground 

 form is a rather flat prism in combination with the clinodomc and the ortho- 

 pinacoid. The most frequent type is the pyroxene habitus; the two pinakoids 

 in equilibrium, prism faces very narrow, and the basal plane; an acute hemi- 



