42 



Scientific Proceedings (87). 



We have developed the technique and tables for preparing 

 hypochlorite solutions at the desired reaction from any bleaching 

 powder, containing more than 20 per cent, available chlorine, in 

 accordance with the following outline. The bleaching powder is 

 decomposed with just enough sodium carbonate to insure com- 

 plete precipitation of all the calcium, the filtrate is neutralized to 

 solid phenolphthalein with dilute (10 per cent.) hydrochloric acid 

 and the solution is then brought to the desired reaction, and a 

 sufficient amount of buffer salts provided, by the addition of a 

 definite volume of sodium bicarbonate solution. 



We have also determined the amounts of carbonate and the 

 technique for preparing hypochlorite solution of the desired 

 reaction from liquid chlorine. We have been assisted in this by 

 two engineering firms who have adopted their chlorine measuring 

 devices to this purpose. 1 The method consists of running chlorine 

 gas into a solution containing a weighed amount of carbonate 

 until the desired percentage of hypochlorite is reached. The solu- 

 tion is then of correct reaction and contains a sufficient amount 

 of buffer. We believe that on the basis of convenience, economy 

 and accuracy that this is the method of choice. 



We have moreover found that the indicator o-cresol-phthalein 2 

 changes color in hypochlorite solutions at about the "ideal" reac- 

 tion and believe we can still further simplify the preparation by 

 its use. 



The methods we have indicated have been in use at our hospital 

 for over two months and have proven themselves to be entirely 

 satisfactory. They have also been found to be of such simplicity 

 that they may be easily mastered. 



1 Wallace and Tiernan Co., New York; The Electro Bleaching Gas Co., New 

 York 



2 Clark, W. M., and Subs, H. A., J. Inf. Diseases, 2, 1, 1917. 



