174 MR. CHARLES A. BURGHARDT ON THE 



manner that granite^ porphyry, phonolite, gneiss, basalt, 

 clay-slate, trachyte, &c. contained a more or less appreciable 

 amount of sodium chloride ; and it is also well known that 

 nearly every spring-water flowing from rocks contains 

 sodium chloride or a chloride of one of the alkaline earths 

 (magnesium chloride). Further, it has been shown by 

 Delesse (Jahrb. f. Min. 1862, 605) that all rocks are satu- 

 rated with water ; and it is also a well-ascertained fact that 

 iron-pyrites (FeS^) is disseminated throughout all crystal- 

 line rocks. Having these facts before me, I made an ex- 

 periment in order to ascertain what reactions would occur 

 on heating iron-pyrites and a solution of cupric chloride 

 together in a sealed tube at a moderately high temperature. 

 Small pieces of pure iron-pyrites were placed in a glass tube, 

 then covered with a moderately strong solution of pure 

 cupric chloride, and the tube sealed up and heated for 14 

 days at a temperature varying from 1 35° to 210° C. ; but the 

 greater part of the time the temperature oscillated between 

 1 50° and 1 70°. On the seventh day the colour of the 

 cupric chloride had become considerably lighter, and a 

 small deposit of violet-red crystalline cuprite was observed 

 adhering to the sides of the glass tube, whilst on allowing 

 the tube to cool it was observed that a very considerable 

 amount of cuprous chloride had crystallized out in beauti- 

 ful transparent colourless tetrahedrons. On the fourteenth 

 day the tube was opened (as no further changes had taken 

 place), and the contents examined, and found to consist 

 principally of cuprous chloride with a small quantity of 

 unaltered cupric chloride, there being at the same time a 

 good amount of ferric sulphate and cupric sulphate present. 

 The deposit on the glass tube was cuprite. I was unable 

 at the time to make any quantitative determination of the 

 various suDstances formed in this reaction, and am there- 

 fore not prepared to say precisely what the reaction was. 



