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Action of Calcium Chlouide Solution on Glass. 



By P. N. Evans. 



In the course of some recent experiments on boiler corrosion the 

 author had occasion to place various dilute solutions in contact with iron 

 wire in glass bottles and heat them in an autoclave containing water up 

 to 200 pounds steam pressure, which corresponds to about 200 degrees 

 Centigrade. The heating was continued for periods ranging from ihree 

 to seven hours. 



The solutions were all about fifteenth-equivalent-normal in strength, 

 and included the following substances, separately: sodium nitrate, am- 

 monium nitrate, calcium nitrate, nitric acid, sodium chloride, calcium 

 chloride, magnesium chloride. In each case 250 cc. of the solution was 

 heated in a 500-cubic-centimeter bottle. 



In most cases the bottles were appreciably attacked by the solu- 

 tions, so that the glass stoppers could not be removed and the bottles 

 were noticeably etched inside, sometimes with the formation of scaly 

 matter on the bottles and in the enclosed water. 



The effect was very much the most pronounced in the case of the 

 calcium chloride. The solution was heated for G hours in a bottle of clear 

 glass of good quality, weighing empty about 275 grams. On opening the 

 autoclave the bottle was found to have been eaten through near the bot- 

 tom and the rest largely covered with a gelatinous layer which hardened 

 in a few days to an opaque coating. The piece of iron wire in the solu- 

 tion throughout the heating had gained very slightly in weight and in 

 tensile strength. Also, about 90 grams of loose scaly material was found, 

 and the solution, which had been perfectly neutral, had become strongly 

 alkaline. Apparently fully half of the glass had been acted upon, so 

 that this very dilute calcium chloride solution, containing less than 1.5 

 grains of calcium chloride, had in about 6 hours chemically attacked 

 over 100 grams of glass. 



In seeking an explanation of the results, the various constituents of 

 a calcium chloride solution may be considered. These include, according 

 to generally accepted modern theories, water, calcium chloride molecules, 



