360 loa Analysis of Pickeringite. 
Arr. XIX.—Deseription and Analysis of Pickeringite, a native 
Magnesian Alum ; by Aucustus A. Hayes. 
Turis mineral occurs in masses, which are composed of long 
parallel fibres, easily divisible, and generally affords rhombic pris- 
matic forms. 'There are numerous cross-fissures, and the fracture 
at these is even. ‘Transparent to translucent, having the satin- 
like lustre of the finest specimens of satin spar, which it much 
resembles. Color white, but when viewed in the direction of 
the fibres, pale rose red, or a delicate green. Taste, like that of 
alum. Sp. gr. 1:78 to 1:80. In dry air it effloresces, in moist air 
it attracts water, and the fibres become flexible. It is soluble in 
cold water, without residue, and the solution has an acid action. 
By chemical analysis, it affords 
Water of crystallization, . ©. ; . 45-450 
Sulpburic acid, . : i é $ .  86:322 
Alumina, ; ‘ i ‘ i . 12:1380 
Magnesia ‘ : 4682 
Protosides of rhengatinse wey ions é : 0-430 
Lim : - ‘ ‘ 0:126 
Hyder eid! ’ é : ‘ : 0-604 
Los : , 0-256 
100-000 
Neglecting the substances, evidently existing in the state of 
mixture with the double salt of alumina, its chemical formula is 
Mg $+.AlS?+422%.* 
In the analysis, bicarbonate of ammonia was used for precipi 
tating the alumina and retaining the larger part of the magnesia, 
in solution with the sulphuric and hydrochloric acids. The pte 
cipitate was ignited, so long as it lost weight; it was then redis- 
solved in strong nitric acid, and its solution was decomposed by 
a large excess of potash solution, The hyduates, insoluble in 4 
ee 
* The water in the above analysis approaches so near 24 atoms, that this is prob- 
ably the amount — in which — it will then conform to the genes ir 
vee one 
ee ee 
alum analyzed b y Wiromeyer. (See Hhthilbaleberg’ s nih con &e. Val 1h 
p- 10; also Dana’s Mineralogy, 2d edition, 1844, p. 554.)— 
ate 
ener ee 
teeta ames 
