1900.] 



on Pottery and Plumbism. 



407 



It will be seen that, provided the ratio obtained by dividing the 

 sum of equivalent percentages of acidic oxides, calculated as Si0 2 

 into the sum of equivalent percentages of basic oxides, calculated as 

 PbO, does not exceed 2, the amount of lead dissolved, whilst in the 

 main tending slightly to increase with the increase of the ratio, seldom 

 exceeds 2 per cent., calculated on 100 parts of the fritt, and that the 

 amount of lead dissolved bears no relation to the quantity of lead 

 present. 



Another fact which came to light was that, provided the ratio of 

 acids to bases is below about 2, the nature of the basic oxides has 

 little or no effect upon the amount of the lead oxide dissolved. This 

 is seen from the following table : 



Table showing that the nature of the basic oxides has little or no effect 

 on the amount of lead oxide dissolved from a fritt by - 25 per cent, 

 hydrochloric acid. 



The solubilities, it will be seen, differ but slightly, although the 

 relative proportion of the basic oxides and their nature vary 

 considerably. 



