162 Co7i}positio7i of Basic Slag 



The principle of the method finally adopted is to shake the slag for 

 a considerable time with carbon-dioxidc-free distilled water, and titrate 

 with standard acid, using phenol-plithalein as an indicator. 



The details of manipulation are as follows. A quantity of slag varying 

 from 1 to 2 grams is shaken for 24 hours in an end over end shaker 

 with 300 c.c. of water freed from carbon dioxide. The whole is then 

 poured into a large Buchner funnel and filtered with pressure. The 

 time taken for filtration is very small, so that the amount of hydrate 

 changed into carbonate cannot be large. The slag is washed back into 

 the flask and the process repeated. In the author's determinations 

 the extractions were continued until the amount dissolved fell below 

 •0008 gram CaO. 



The method probably gives results that are somewhat too low, owing 

 to the conversion of a small amount of the hydrate into carbonate during 

 the process of filtration, although this is probably compensated for to 

 some extent by the fact that other calcium compounds in the slag are 

 also to a small extent attacked, as it seemed impossible by continued 

 extraction to obtain a solution which was not slightly alkaline to phenol- 

 phthalein. 



The point which the author adopted as the limit was usually reached 

 at the third extraction. 



Four determinations of lime in the same slag gave the following 

 results : 



5-0o \ 



5-24 

 0-22 



5-99 j 



-percent, free lime. 



It was considered that the results were close enough to make the 

 method a useful one. 



In the four samples of slag considered the percentages of CaO were 

 as follows : 



A. 4-69 



B. 5-29 



C. 1-28 



D. 5-37 



The numbers being rather lower than was expected it was suggested 

 that this might be owing to the conversion of some of the oxide into 

 carbonate as the result of storage. 



Determinations wore nuide of the carbonate present by the method 



