( ]7 ) 
VII. Ext raft of a Letter from M. Geoffrey, 
Chemift, Member of the Royal Acade- 
my of Sciences at Paris, and F. ^ 5. to Sir 
Hans Sloane, 'Bart. Brefident of the Royal 
Society $ concerning Mr. Seignette’* Sal Pc- 
LYCHRESTUS RuPELLENSIS, and fome 
other Chemical Saits. By T. S. M D. 
Paris, May 4, 1732. 
SIR, 
* ^ . 1 
W E have nothing new in Chemijlry here, but 
the Difcovery we have made of the M;ike of 
Meil' r! . Seignette' s Sal polychrejus Rupellenfis. 
It is a T art arum foluhile, compofed of Cream, or 
Cryfhls of Partar ; and the fix'd Salt of the Kali 
of Alicante well depurated. This Salt is very lin- 
gular ; for tho’ it be a fix’d Alkaline Salr, it has the 
peculiar Property of cryflalizing; nor daps it ea lily 
diflblve in the open Air, as other fix’d Salts do } but on 
the contrary, it calcines therein, like Kitriofs or Gian • 
her' s Salr. Another peculiar Property, which I have 
obferv’d to belong to it, is, that if it be fatiated with 
a vitriolick Acid, and the Liquor be evaporated, 
there refults a Salt that has the Form of Glauber’s 
Salt, and all the Properties requifite to make MelPY 
Seignette' s Salt, In order to which, 
Take 
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