Eaklb.] 



Palacheite 



235 



CHEMICAL PROPERTIES. 



Pyrognostics, — The mineral strongly exfoliates, like stilbite, 

 before the blowpipe, and is converted into an Infusible brownish 

 black, magnetic mass. Much water is given off in a closed tube, 

 which does not react acid unless the heat is high enough to 

 decompose the sulphate. It is difficultly soluble in cold water, 

 but when the solution is heated it becomes decomposed with the 

 separation of a bulky, yellowish red precipitate of ferric hydrox- 

 ide. The mineral is easily and completely soluble in dilute acids. 

 It is perfectly tasteless. 



Composition . — The average of several analyses of the mineral 







Molecular 

 Ratio. 



Approx. 

 Ratio. 



Fe L .0 :l 



19.51 



.122 



1 



MgO 



9.35 



.239 



2 



so :i 



38.37 



.480 



4 



H 2 at 100° C 

 EUO above 100° C 



19-53 U 9 2g 

 12.75 8 



99.51 



1.793 



15 



The formula, therefore, is Fe 2 3 .2MgO .4S0 3 + 15H 2 0, and this 

 requires the following percentages, which correspond very well 

 with the analysis: 



Fe,0 3 19.28 

 MgO 9.64 

 S0 3 38.55 

 H 2 32.53 



100 



A fractional water determination was as follows: 



At 100° C 19.53 



160 6.12 



220 3.52 



270 1.34 



Above 280 1.77 



32.28 



All of the water could be driven off without decomposing the 

 sulphate. About nine molecules were lost, at 100° C, thirteen at 

 about 270°, and the remaining two probably near 300? Twenty 

 per cent, of the water driven off at 270° was reabsorbed over 

 night by exposure to the air, and enough moisture was absorbed 

 after several days to render the powder a pasty mass. 



