1857.] of Gold (and other Metals) to Light. 41 1 



Diffused particles of gold -production proportionate size 

 colour aggregation and other changes. 



Agents competent to reduce gold from its solution are very 

 numerous, and may be applied in many different ways, leaving 

 it either in films, or in an excessively subdivided condition. 

 Phosphorus is a very favourable agent when the latter object 

 is in view. If a piece of this substance be placed under the 

 surface of a moderately strong solution of chloride of gold, 

 the reduced metal adheres to the phosphorus as a granular 

 crystalline crust. If the solution be weak and the phosphorus 

 clean, part of the gold is reduced in exceedingly fine particles, 

 which becoming diffused, produce a beautiful ruby fluid. 



This ruby fluid is well obtained by pouring a weak solution 

 of gold over the phosphorus which has been employed to 

 produce films, and allowing it to stand for twenty-four 

 or forty-eight hours ; but in that case all floating particles 

 of phosphorus should be removed. If a stronger solution 

 of gold be employed, the ruby fluid is formed, but it soon 

 becomes turbid and tends to produce a deposit. When the 

 gold is in such proportion that it remains in considerable 

 excess, still the ruby formation is not prevented, and being 

 formed it mingles unchanged with the excess of gold in 

 solution. If an exceedingly weak solution of gold be em- 

 ployed the production of ruby appears to be imperfect and 

 retarded. The nearer the solution is to neutrality at the 

 commencement the better ; when a little hydrochloric acid was 

 added the effect was not so good, and the colour of the fluid 

 was more violet than ruby. 



If a pint or two of the weak solution of gold before described 

 be put into a very clean glass bottle, a drop of the solution of 

 phosphorus in sulphide of carbon added, and the whole well 

 shaken together, it immediately changes in appearance, becomes 

 red, and being left for six or twelve hours, forms the ruby 

 fluid required ; too much sulphide and phosphorus should not 

 be added, for the reduced gold then tends to clot about the 

 portions which sink to the bottom. 



Though the sulphide of carbon is present in such processes 

 and very useful in giving division to the phosphorus, still it is 

 not essential. A piece of clean phosphorus in a bottle of 



