Reiser & Forder — Determination of Free Lime. 167 



These results show that the method is quantitative and that 

 lime that has been heated to the highest temperature attainable 

 in a platinum crucible with the blast lamp is completely slaked 

 in twenty minutes at 85 degrees. In fact in the case of pure 

 quick lime the slaking is very rapid. The calcium hydroxide 

 was found to be constant in weight up to 250 degrees, beyond 

 which it was not tested. The calcium hydroxide when 

 exposed to the air, of course takes up carbon dioxide. It is, 

 therefore, necessary to keep the crucible in a desiccator con- 

 taining caustic potash instead of calcium chloride and to 

 weigh as rapidly as possible. 



HYDRATION OF COMJIERCIAL LIME. 



For the determination of calcium oxide in commercial quick 

 lime a large piece was taken and the exterior portions broken 

 away and a sample for analysis taken from the interior of 

 the lump. This was quickly placed in a tightly stoppered 

 weighing tube. Portions of this were weighed off in a plati- 

 num crucible and then water was added in a little greater 

 quantity than was necessary for slaking, the crucible put 

 into the protector warmed to 85 degrees for some minutes 

 and then a slow current of air free from carbon dioxide 

 drawn through for half an hour, the temperature now being 

 raised to 185 degrees. After cooling in the desiccator the 

 increase in weight was determined and from this the percent- 

 age of lime in the sample calculated. The following results 

 were thus obtained : — 



