434 M. Stromei/er on Poll/halite. [Dec. 



ness, and this experiment I repeated several times with equal 

 care, in order to convince myself whether the proportion of 

 water was uniformly similar, or at all varied. 



That they may be more easily compared together, I have 

 given the experiments and their results in the following table : 



Number 

 of ex- 

 peri- 



iDects 



1 



II 



III 



IV 



V 



VI 



VII* 



VIII* 



Quantity of 

 poljhalite 

 calcined. 



3-149 

 6-660 

 5-573 

 5-651 

 5-000 

 5-921 

 3-692 

 4-4515 



o-rm 



Weight of the 

 residuum. 



2-958 

 6-257 

 5-224 

 5-303 

 4-695 

 5-554 

 3-472 

 4-1885 



grm 



The loss of 

 weight ow- 

 ing to cal 

 cinatioD. 



191grm, 



0-403 



0-349 



0-348 



0-305 



0-367 



0-220 



0-263 



The quantity 

 of water thus 

 shown in 100 

 partsof poly- 

 halite. 



6-0654grm. 



6-0515 



6-2623 



6-1582 



6-1000 



6-1982 



5-9588 



5-9081 



The average. 



1 



{► 6-13927 



I 

 I 



J 



I 5-9335 



It is very obvious from these experiments that the quantity of 

 water contained in polyhalite does not vary,t but is subjected 

 to certain determinate proportions. Hence it is evident that the 

 water is not fortuitous, but constitutes an essential part of its 

 nature, and, as we may conclude from the appearance of the 

 mineral during ignition, enters it along with a portion of sulphate 

 of hme forming the gypsum. 



But since 21 parts of water are contained in 100 of gypsum, it 

 is sufficiently apparent from these experiments, reckoning the 

 quantity of water which, with the sulphate of lime, produces the 

 gypsum, according to the average of Experiments VII. and 

 YIII.when,aswehaveobserved,the mineral had contracted some 

 moisture from the atmosphere, that in 1 00 parts of polyhahte 

 there are 28-2548 of gypsum, or sulphate of lime united with 

 water. 



(B.) 



a. 5-045 grm. of this fossil reduced to a very fine powder with 

 twice that quantity of crystalUzed carbonate of soda dissolved in 

 a proper quantity of water were boiled for half an hour ; and, 

 to prevent any of the powder from adhering to the sides of the 

 Tessel, were kept continually stirred during the whole operation. 

 After which the liquor, while yet hot, was purified by filtration 

 from any remaining powder, and the residuum well washed in 

 boihng water. 



• The moisture contracted from the atmosphere having been previously ab- 

 sorbed. 



+ The slight variations observable in my experiments were occasioned by the 

 moisture which the mineral had contracted from the atmosphere. 



