322 PROCEEDINGS OF THE ACADEMY OF [1880. 



from the total water, ^.5S per cent., giA^es for water of cr3'stalliza- 

 tion, 4.34 per cent. As will be seen below, a similar amount is de- 

 duced from Mr. Haines' experiments. 



The following experiments by Mr. Haines have been kindly 

 placed at the disposal of the writer. They may be relied upon as 

 having been performed with great care. 



I. The powdered mica is placed in a desiccator over concen- 



trated sulphuric acid. 



(a) Dried 15 days. Loss, 2.69 per cent. 



(b) " 10 " " 2.89 " 



II. The undried mica is heated in an air-bath at 100° C. 



(a) Heated 3 hours. Loss, 3.14 per cent. 



(b) " 3.33 " 



(c) " 3.42 " 



(d) " 51 " " 3.69 " 



Weights. Per cent, of loss. 



III. Weight before heating. 1.0880 



Heated at 100°, 1| hours. 1.0613 2.46 



" " 4i " 1.0598 2.59 

 Over H2SO4 and heated 5 hours 



at 100°. 1.0558 2.96 



Heated 2 hours at 100° and 



cooled over H,SO,. 1.0613 2.46 



"Weight. Total Loss from Inere- p.c. ofp.e. ol 



loss. 100° C. ment total loss fr. 



ofloss. loss. 100°O 



lY. Weight before heating. .9035 



HeatedatlOO° C. for Ihr. .8743 .0292 3.23 



" * 100° " 2 " .8730 .0305 3 37 



" 105° " 2^" .8715 .0320 .0015 .0015 3.54 0.15 



" 119° " 1 " .8705 .0330 .0025 .0010 3.65 0.28 



" full red heat 5 mill. .8350 .0685 .0380 .0355 7.58 4.34 

 " over blast lamp 



1st time. .8270 .0765 .0460 .0080 8.46 5.27 

 " over blast lamp 



2d time. .8280 .0755 .0450 8.35 5.15 



