382 



7 Similar to isobiitylaleohol is the behaviour of various other 

 solvents such as amylalcohol, l)enzene, lightpetroleum, carbon tetra- 

 chloride, carbon disulphide and ether ^). 



8. Goldsolutions prepared in another way (for instance by electric 

 dispersion of gold wire, or by reduction of AuCP with a solution 

 of phosphorus in ether) and having a red or reddish-violet colour 

 behaved in the same manner; the gold was deposited with a blue 

 colour at the surface of contact. ^Somewhat different was the 

 behaviour of a brownish coloured solution recently prepared from 

 AuCP and solution of phosphorus in ether, for this was quite 

 indifferent to ether and no gold was deposited at the contact surface. 



9. In order to attain the equilibrium from the other side also, 

 it was endeavoured to prepare a colloidal solution of gold in 

 another dispersion medium. This succeeded in butyl or amylalcohol 

 and in ether, both by electric dispersion of gold wire at a low tem- 

 perature and by reduction of AuClg in these solvents by a solution 

 of phosphorus in the same medium. By electric dispersion could also 

 be obtained reddish solutions; those prepared by reduction with 

 phosphorus had a yellowish-brown colour. 



On shaking with water the gold in the first solutions passed into 

 the surface of contact. The yellowish-brown amylalcohol solution 

 was quite unaffected by shaking with water; not a trace of gold 

 found its way into the water or collected at the surface of contact. 

 This solution was also very stable in otlier respects and could be 

 boiled without undergoing any change. 



It thus appeal's that the gold of the yellowish-brown amylalcohol 

 solutions is stable with regard to the aqueous phase. On the other hand, 

 the gold from the red and reddish- violet solutions is stable in the contact 

 layer. When, as is very probable in the case of colloidal silver, the 

 differences in colour must be attributed to a difference in the size 

 of the gold particles present we should have here a case of the 

 possibility suggested in 4. 



The yellowish-brown solution of gold in ether is very unstable. 



however, the lube containing the liquids is placed in an inclined position the gold 

 will somewhat lag behind the liquid and it appears that the phase is colourless. 

 2) Carbon disulphide in presence of water forms the bottom layer; this is 

 entirely surrounded by a splendid blue coloured golden skin, which has collected 

 at the place of contact of the carbon disulphide and the water ; a very beautiful 

 demonstration of the fact that water penetrates between the glass and the carbon 

 disulphide. When shaking, every drop of carbon disulphide is coloured blue by 

 gold adhering to the surface and thus it looks as if the liquid itself possessed 

 that colour; by removing some with a pipette it will be seen that such is not 

 the case. 



