132 On the maniffacturiiig, cm a large Scale, 



vitrification, as M. Van Mons thinks*; for it would fol- 

 low, if this oxide were really half vitrified by this ope- 

 ration, that a higher temperature would be capable and 

 ought necessarily to convert it into glass ; but nothing of 

 the kind takes place; for I have exposed to a very strong 

 heat, and at several times, four granmies of this oxide, well 

 crystallized, in two crucibles luted together, and, instead of 

 vitrifying, it lost not only its brilliancy but also its fine red 

 colour, and acquired one of a disagreeable brick red. Ex- 

 posing it to a still greater heat, a great part of it was reduced, 

 and the rest of the oxide acquired a dark brown colour. 



" I know, however, that there are bodies which are not 

 susceptible of passing to complete vitrification, and which 

 nevertheless experience, at a certain degree of heat, a paste- 

 like fusion which is called senii-vitriform ;. but by heating 

 the oxide of mercury in transparent vessels nothing similar 

 is seen to take place, not the least vestige of a partial or 

 general softening of the mass is observed. Besides, I have 

 strong reasons for believing that the crystalline state of the 

 mercury oxidated by nitric acid arises only from the degree 

 of the oxygenation of that metal, and the uniform manner 

 in which the oxidating principle combines with the mer- 

 cury during the decomposition of the nitrate of that basC), 

 and its conversion into red oxide." 



XX. Second Extract from a Memoir oj" M. Paysse, prin- 

 cipal Preparer of Medicines at the Camp of Utrecht, on 

 the Method of mamfacturbig, on a large Scale, some 

 Oxides of Mercury. By M. PAKMENXiERf. 



iNoTHTNG remains, in order to make known the memoir 

 of M. Paysse on the oxides of mercury, but to give a short 

 view of the other experiments he made in regard to the red 

 oxide of mercury by nitric acid (red precipitate) : they form 

 the complement of his process given in the preceding ar- 

 ticle. If this process be followed, it will remove all the un- 

 certainty of manufacturers who hitherto have not been able 

 to prepare this substance as is done in Holland. Every 

 thing is easy in theory ; but in the arts facts speak much 

 better than the most brilliant reasoning. 



To ascertain that the crystalline state of the red oxide of 



* Journal ile Physique et de Chimie, nances 10 et 12, pages 178 et 211. 

 f From the Journal dc Chbiiie, No. 154. ' 



mercury 



