2Q2 PHILOSOPHICAL TRANSACTIONS. [ANNO 1 782. 



shining crystals. When exposed to the weather, gets an ochry colour on the 

 outside ; strikes fire with steel ; cuts glass ; melts, though not easily, under the 

 blow-pipe. Heated in an open fire, becomes magnetic, and loses about 3 in 100 

 of its weight. 



Exper. — a. after 3 drs. had been broken to small pieces with a hard steel 

 hammer, on a plate of the same metal, it was ground to an impalpable powder 

 in one of Mr. Wedgevvood's China mortars. The mortar, which had been 

 previously weighed, lost only ■£■ of a grain weight during this operation. 



B. This powder was repeatedly washed with pure water, so as to carry oft' all 

 the finer parts, and the coarser ground again, till the whole was washed awav. 

 The washings were then filtered, and the powder carefully collected and dried. The 

 water employed in the washings did not appear to have dissolved any part of the 

 stone ; for no precipitate was formed either on the addition of mild fixed alkali, 

 or of silver dissolved in the nitrous acid. 



c. 100 parts of this powder were put into a small mattrass, arid covered with 

 marine acid: a degree of heat was excited, and a very slight effervescence took 

 place. Water was then added, and the mixture kept boiling for half an hour. 

 The liquor was decanted off, and more acid added, which was boiled as before. 

 This was decanted, and the residuum washed with water till the water came off 

 tasteless. These waters were added to the liquors before decanted. The powder 

 had now an ash-coloured appearance, and when dried weighed 80|. To the 

 liquors (c) phlogisticated fixed alkali was added, till no more Prussian blue was 

 precipitated. To effect this, it took I oz. 5 drs. 12grs. of the phlogisticated 

 alkali. The precipitate, when washed and dried, weighed 47- 



e. The powder of 80-J- (c) mixed with twice its weight of fossile fixed alkali, 

 was put into a black lead crucible, and exposed to a red heat for 2 hours. The 

 heat was never sufficient to render the mass fluid, nor to make it adhere firmly 

 to the crucible. The saline part was then washed away by repeated effusions of 

 hot water. To the remaining powder marine acid was added repeatedly, and 

 boiled as before. The powder was now perfectly edulcorated by hot water, and 

 when dry weighed 47 \. The above liquors were all added to the liquor (c), and 

 phlogisticated fixed alkali was dropped in, till no more Prussian blue was precipi- 

 tated. To effect this, \ oz. of the alkali was required. This precipitate weighed 

 1Q; so that the whole of the Prussian blue weighed 66. After calcination 

 in a crucible it was reduced to 31^, and was then wholly attracted by a magnet. 



f. Mild fixed alkali was now gradually added to the liquors after the sepa- 

 ration of the Prussian blue, and a white powder was precipitated. This powder, 

 when well washed and dried, weighed 46^. After being exposed to a low red 

 heat for lO minutes, it weighed only 32J-. 



