Allen and Clement — Role of Water in Tremolite. 105 



fine powders are known to absorb moisture from the air.* 

 The crucible containing the powder was introduced into the 

 furnace, rapidly heated to the required temperature and kept 

 there during the rest of the working day. Then it was quickly 

 transferred to a sulphuric acid desiccator, cooled and weighed. 

 The time of cooling was usually about 20 minutes. There is 

 some chance of error here, in that the mineral may, have 

 absorbed moisture or air during the cooling. Friedelf found 

 that a nearly dehydrated chabazite absorbed 2'34 per cent of 

 air when left in a desiccator several hours. Such errors must 

 be small in tremolite, for the time of cooling seemed to make 



S 



























s 



























c 



























CO 



co 



C 



















































30 



20 





















' 



) 





























IO 









O 



















400 600 800 IOOO 



Y. The 



losses are too small but the form of the curve will be seen to resemble closely 

 those in fig. 3, where the work was more exact. 



Temperature. 200 

 Curve showing loss of water in tremolite from Gouverneur, N. 



.no difference in the apparent weight and the substance did not 

 show a tendency to gain on the balance except after heating at 

 the lower temperatures where the losses were small. 



The heating at each temperature was continued until prac- 

 tically constant weight, i. e., until the loss in 5-6 hours was not 

 more than 1-3 tenths of a milligram. 



Curves showing loss of water with temperature. — The first 

 work was clone on the tremolite from Gouverneur, N. Y. The 

 results are plotted in fig. 2. It was afterwards found that the 

 work was quite imperfect because, instead of heating to a 

 constant weight, what was considered an ample period of time 



* Day and Allen, this Journal, xix, 127, 1905. Mauselius, Arsbok Sver- 

 iges Geologiska Undersokning No. 3, 1907. W. F. Hillebrand, private 

 communication. Much more complete treatment in paper about to be pub- 

 lished. 



I Bull. Soc. Mm., xxii, p. 15, 1899 ; see also Hillebrand, loc. cit., p. 50. 



