136 The Philippine Journal of Science mi 



In order to obtain finely divided gold, gold chloride solution 

 was treated with oxalic acid. While this precipitate was still 

 in suspension, gogo was added. It had apparently no effect upon 

 the physical condition of the gold, which settled with the same 

 rapidity and had the same color as gold precipitated by oxalic 

 acid alone. 



Further tests were made to determine if gogo in any way 

 increased the adhesion between gold and wood or the cohesion 

 between gold particles, but no change was noted. It also failed 

 to reduce the surface tension of water to any noticeable extent, 

 or to clean the gold by cutting the oil upon it. 



The above tests show that gogo has no qualities which would 

 be beneficial to the concentration of gold and it would be actually 

 harmful where amalgamation is used. Apparently its only 

 agency is the effect of the spray of solution falling on the float- 

 ing particles of gold in the pan and causing them to sink. Water 

 sprayed in the pan would have the same effect. On the other 

 hand, the tests indicated that gogo is detrimental where amal- 

 gamation is used, and its only apparent quality is to hold fine 

 particles in suspension, an effect just opposite to that desired. 



In making the test on finely divided, precipitated gold it was 

 found that if gogo were added to the gold chloride solution before 

 oxalic acid, or before precipitation had taken place, purple solu- 

 tions were obtained which appeared to be colloidal gold. While 

 such an investigation rightly belongs in the field of physical 

 chemistry, it was decided to make a few tests on the formation 

 of colloidal gold solutions by means of gogo, with the hope 

 that they might prove of value as a basis for a more thorough 

 research. 



Zsigmondy 2 states in regard to forming colloidal gold, that — 



the chief essential is distilled water of sufficient purity, and the absence 

 of electrolytes is not so essential as the absence of colloids. Traces of 

 the former will do no harm, seeing that a certain quantity of them is 

 introduced into the water by the reagents themselves. On the other hand, 

 traces of colloids, almost always present in all commercial distilled water, 

 completely prevent formation of bright red gold hydrosols. 



Therefore, it was interesting to discover that colloidal gold 

 solutions could be made in the presence, and by means, of colloids. 



The gogo was extracted from the gogo bark, which is obtained 

 commercially in the Philippine markets, by allowing the bark to 

 soak thoroughly in distilled water for five or ten minutes and 



2 Colloids and the Ultra-microscopic. 1st ed., J. Wiley & Sons, N. Y. 

 (1909), 124. 



