88 University Geological Survey of Kansas. 
was the more pronounced, and Chatelier regarded these interrup- 
tions as due to an absorption of heat which accompanied the 
elimination of water. ‘This would indicate the existence of two 
different hydrates, whose decomposition took place at the tem- 
peratures indicated by the halts on the chronograph. Further, 
the dehydration was found to be incomplete at 155° C., or 311° F., 
and complete at 194° C., or 381° F. 
In order to prove the composition of the first hydrate, Chate- 
lier heated a saturated solution of gypsum in a closed tube to a 
temperature between the two halts indicated, or between 130° C. 
(266° F.) and 150° C. (302° F.), and very delicate, long, rec- 
tangular prisms were formed, which were thrown into alcohol, 
and then analyzed, with the following result : 
Wie COT eee ee FUT er ATOR oe NSH NSEC a 6.7 per cent. 
Gass 
3 66 66 
100. 
This agrees very closely with the formula (CaSO,),, H.O, 
where there would be 
AWiAGET litt cute te), rircirceeE crete is ane aie gaa 6.2 per cent. 
Sulphatevof, lime cya cp ee eae Unetrane ae By nis) 108, SS 
100. 
In this compound it is seen that two parts of lime sulphate 
are united with one part of water, while in the original gypsum 
one part of ime sulphate was united with two parts of water. 
Chatelier also found that the incrustation in the boilers of ocean 
steamers, where salt water was used and where the temperature 
averages about 165° C. (320° F.), possessed nearly the same 
composition as the hydrate given above. His analysis was as 
follows : | 
ninve; Carbonate 2% ees oe ee ee ee . 0.3 per cent. 
PTOMOXIM Oe. ees nae aon cae URL URE ea OTR Di OUR Sra weaes 
Wie GOT: 2S ies cicea ie eps Na cipt Uane one Me a eR ee RIM DAS aiaeanince 
simeisulplia tence re ceils He een cectsaee tea eae genet SOS Yea OU en IO 
100. 
Further experiments by Chatelier showed that if ten grammes 
of powdered gypsum were heated for some time at 155° C., or 
311° F., intermediate between the temperatures necessary for 
the decomposition of the two hydrates, the loss in weight was 
