On the Aerated Barytes. 607 



The Aerated Barytes is in general of a pale 

 greyifh white colour, but fometimes it inclines to 

 the milk white, and at others has a flight yellowifh 

 tinge, which is a token of the prefence of Iron. 



It is found in folid mafles, fometimes filling 

 the whole of the vein, at others interfperfed 

 amongft the Vitriolated Barytes ; the mafles are 

 generally rounded on the outfide, and afFed: fome- 

 thing of a globular form. It^ is feldom found 

 externally cryfliallized : I have however obferved 

 four varieties of it in that ftate. The one in which 

 a number of fmall Cryflials radiated in the form of 

 a fl:ar from a centre j thefe Cryftals were about 

 half an inch in length, very thin, and appeared to 

 be hexagonal columns rounded to a point. The 

 other varieties were the fix-fided column, pointed 



fourth volume of the Annates de Chimie, attributes without 

 any fufficient grounds, to the difengagement of fixed air. 

 If on the contrary, " contains^* be intended to denote a Me- 

 chanical mixture, or adhefion of the Arfenic and Lead to the 

 Aerated Barytes, I apprehend this alfo to be a miftake, as 

 among all the fpecimens which I have feen, I have never 

 yet been able to deteft Arfenic under any form whatever. 

 I imagine the Martial Pyrites has been miftaken for Mif- 

 pickel ; but the Arfenical part of Mifpickel not being fo- 

 luble in the marine acid, can be of no prejudice in pre- 

 paring the Muriated Sale, and it is hardly poflible to con- 

 found either it, or Blue Lead Ore with Aerated Barytes. 



I have thought it neceflary to make the above remarks, 

 that the idea of fo fimple a medicine being liable to con- 

 tain fuch poifonous metals, might not render medical men 

 nnneceffarily fcrupulous in prefcribing, or deter patients 

 from taking it. 



with 



