n6 THE NEW WORLD OF SCIENCE 



and the Bureau of Standards assisted in the inspection of the 

 product. In December, 1917, the Geophysical Laboratory also 

 took entire charge of the plant of the Spencer L?ns Company 

 and with a free hand was soon making glass equal to that from 

 Jena. 



Assistance of the utmost importance was brought to bear 

 upon the glass problem from other quarters. The Geological 

 Survey put men into the field to find suitable sand, limestone, 

 and clays, and were successful. Sand of high chemical purity 

 and composed of uniformly small grains was secured at Rock- 

 wood, Mich. ; Hancock, Md. ; and Ottawa, 111. Interesting 

 experiments were conducted on the removal of iron from other 

 sands by the use of chlorine and later phosgene, but this method 

 of treatment proved to be too costly, and in the meantime sand 

 sufficiently free from iron was found. Potassium carbonate 

 of necessary quality was produced by Armour & Company, 

 who deserve credit for the excellent work done on this impor- 

 tant raw material. In some glass sodium could be substituted 

 for potassium, but in certain cases the glass is inclined to be 

 less brilliant. 



Good sodium carbonate, barium carbonate, boric acid, zinc 

 oxide, arsenic trioxide, and precipitated calcium carbonate were 

 finally secured. Lead oxide with less than 0.02 per cent, iron 

 oxide was also secured and by exercising careful chemical 

 control, no great difficulty was experienced with raw materials. 



Pots have been mentioned, but we must emphasize their real 

 importance. Poor pots can cause all manner of trouble, rang- 

 ing from breaking at critical points and necessitating the re- 

 building of a furnace, to dissolving to a detrimental degree in 

 the glass melt. The Pittsburgh Plate Glass Company was 

 already accustomed to making special pots, and in June, 1917, 

 began experiments involving feldspar as an ingredient. While 

 their work was in progress the Bureau of Standards was suc- 

 cessful in devising unusually good pots for optical glass. This 

 work was under A. V. Bleininger, who also devised a successful 

 method for casting pots. Most of the pots are 36 inches in 



