132 NEW YORK STATE MUSEUM 



continues up to 204° C. The most extensive experiments, how- 

 ever, were probably made by Le Chatelier.^ As a result of these 

 experiments, it was discovered that from the boiling point 

 of water up to 200 °C., the rise in temperature was constant 

 with two exceptions. The first halt occurred at 128 °C., the sec- 

 ond at 163 °C. From this fact and the fact that water ceased 

 to pass off at these stops, he inferred that there are two dif- 

 ferent hydrates which are decomposed before any rise in tem- 

 perature takes place. 



In order to prove the existence of two hydrates, Le Chatelier 

 heated a saturated solution of gypsum in a closed tube to a 

 temperature between 130°C. and 150°C. As a result, delicate 

 rectangular prisms were formed, which, when analyzed, gave 

 the following result: 



Water 6.7 



Sulfate of lime 93.3 



100 



A result was obtained in this way which corresponds very 



closely to an analysis of the incrustation in the boilers of ocean 



steamers, in which the analysis made by Le Chatelier was as 



follows: 



Lime carbonate .3 



Iron oxid 2 



Water 5.8 



Lime sulfate 91.9 



100 



These results both agree very closely with the formula 

 (CaSO^)^ H2O, which would show the analysis 



Water 6.2 



Sulfate of lime 93.8 



100 



^Le Chatelier. On the Dehydration of Gypsum stone and the two Com- 

 pounds Formed. Academie des sciences. Comptes rendus. 1883. 



