i 24 On the mamifacturirrg, on a large Scale f 



tention ; and, after comparing them with those published 

 by M. Tuckert in the fourth volume of XhtAnnales de Chi- 

 viie, for the year 1790, he found only a very slight differ- 

 ence; so that the description of the chemist of Amsterdam 

 may be considered as nearly exact. The following is what 

 he has omitted. He does not speak of the duration of the 

 flame, nor of its colour, which arises from the combustion 

 of the union of the sulphur and mercury previously pre- 

 pared and introduced into the apparatus. This flame, the 

 disengagement of which is exceedingly rapid, exhibits the 

 most various colours ; first of a bright dazzling white, rising 

 at least twelve decimetres above the dome of the furnace ; 

 then yellow and while orange yellow ; blue and yellow, giv- 

 ing birth to the green and violet shades, and at last to blue 

 and to green. Its disengagement is overcome towards the 

 end by a sort of register of iron plate_, when it no longer 

 rises but to the height of some centimetres, and its colour 

 becomes indigo or sky blue. The apparatus is then her- 

 metically sealed, and luted on the outside with a mixture 

 of clay and sand. 



There is no doubt, from the loss experienced in the result 

 of the operation, that the shades so various of this flame, 

 the disengagement of which lasts about half an hour with 

 200 kilogrammes of matter, arise from the union of the 

 sulphur with varied proportion of mercury at different de- 

 grees of oxygenation. The 400 kilogrammes, or about 800 

 pounds of red sulphurated oxide of mercury, were reduced 

 to 379 or 322 kilogrammes, or between 738 and 743 

 pounds, which form a loss of from 27 to 31 kilogrammes. 

 In speaking of the vessels employed in this operation 

 M- Tuckert forgot also to describe exactly their form. The 

 principal vessel is not a jar, but a kind of crucible, round 

 which the heat circulates, and which has over it an iron 

 dome, through the summit of which the matter is intro^ 

 duced after the crucible has been brought to a red heat. 

 The success of the operation depends in an essential manner 

 on the management of the fire during the sublimaiion. The 

 fuel employed is turf, and, according to M. Paysse's ob- 

 servation, none is better calculated for the purpose when 

 3 constant and moderate heat is required. This unifonnity 

 of temperature during the thirty hours of heat maintained 

 m the furnace is, no doubt, one of the causes which contri- 

 butes most to the success of the operation. Besides, expe- 

 rience, according to the acknowledgment of the workmen, 

 Kppaks in favour of this opinion. 



Whei) fed sulphurated oxide of mercury is \ repared, a 



very 



