Chemical Notices : — Van der Kolk on Chemical Combinations. 433 



If, therefore, sulphate of iron, in a solution containing gold, 

 should become transformed by the action of a reducing agent 

 into pyrites, the gold, at the same time being reduced to the 

 metallic state, would probably be found enclosed in the resulting 

 crystals of that mineral*. 



(g) The silica and other substances forming the cementing 

 material of the ancient auriferous river-beds have probably been 

 slowly deposited from comparatively cold solutions. 



(h) The connexion existing between the decomposition of 

 felspar by the agency of boiling springs, the existence of alka- 

 line plains, and the formation of lakes containing various salts 

 of soda and potash will be at once obvious to the geologist. 



LIII. Chemical Notices from Foreign Journals. 

 By E. Atkinson, Ph.D., F.C.S. 



[Continued from vol. xxxv. p. 461.] 



SCHRODER VAN DER KOLK published shortly before 

 his death two articles in PoggendorfFs Annalen, vol. cxxxi., 

 of which the following is an abstract taken from the Zeitschrift 

 fur Chemie. 



If a body be heated from zero to a given temperature, it takes 

 up a certain quantity of heat which is consumed in increasing its 

 temperature and for internal and external work. If, from the heat 

 taken up, heat which has been transformed into external work be 

 subtracted, the remainder represents the heat contained in the 

 body after the process ; and this quantity is called the mechanical 

 energy of the body in this condition. Hence, in a definite con- 

 dition, every body possesses a certain quantity of energy ; the 

 absolute quantity of energy is always unknown. 



* From a somewhat lengthy investigation of the subject, I am induced 

 to believe that gold invariably occurs in pyrites and other sulphides in the 

 metallic form. Tarry matter, like that found in the solfatara at Borax 

 Lake, has occasionally been met with in the quartz veins of California ; and 

 although the protosulphate of iron, resulting from the decomposition of the 

 sesquisulphate, would, under certain circumstances, have the effect of pre- 

 cipating gold from solution, it would probably not do so in the presence of 

 large quantities of the persalts of that metal. A discovery, made by Mr. 

 Daintree, of the fact that a speck of gold lying in a solution of the chloride of 

 that metal may be increased to several times its original weight by the action 

 of a small piece of cork introduced into the solution, is recorded by Mr. 

 Ulrich. Mr. Wilkinson's experiments further prove that, besides gold itself, 

 iron, copper, and arsenical pyrites, galena, blende, &c. likewise form fa- 

 vourable nuclei, which, if immersed in weak solutions of chloride of gold, 

 receive a solid coating of metal by the agency of organic matter, such as a 

 chip of wood floating in the solution. — ' Notes on the Physical Geography, 

 Geology, and Mineralogy of Victoria' (antecit.), p. 44. 



Phil. Mag. S. 4. Vol. 36. No. 245. Dec. 1868. 2 F 



