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USEFUL 



PROJECTS AND IMPROVEMENTS. 



Montgolfier's Process for making 

 White Lead. By Messrs. Cle- 

 ment and Desormes. 



THE first operation consists in 

 forming the lead into sheets. 

 He found from experience, that 

 by running the metal on ticking, 

 the sheets might be made of any 

 thinness, and varied at will, by 

 inclining the frame a little more 

 or less. The surface then becomes 

 a little irregular, and full of points; 

 which is favourable to the oxida- 

 tion that follows. On this opera- 

 tion we need not insist, the process 

 being already well known. 



The second operation consists in 

 oxidizing and carbonizing the lead. 

 The following is the disposition of 

 the aparatus : — 



M. Montgolfier had a common 

 chemical reverberatory furnace, in 

 which he burned charcoal. The 

 chimney on its dome was four or 

 five metres high, and, taking a 

 horizontal direction, was intro- 

 duced into an opening in the end 

 of a cask (which lay on its side) 

 a little above its centre. Some 

 vinegar was put into the lower 

 part of this cask, and towards the 

 centre of its other end was adjusted 

 another tube,eqi)al to the chimney, 



and communicating by its other 

 extremity with a large rectangular 

 case in which were suspended the 

 sheets of lead alternately high 

 and low, that the air might pass 

 entirely over their whole surface. 

 The other end of this case had an 

 opening to allow the redundant 

 gas to escape. The case had a 

 cover, which could be removed at 

 pleasure, for the purpose of placing 

 the sheets of lead on small pieces 

 of wood prepared to receive them. 

 The air from the furnace, being 

 thus made to pass through the cask 

 containing the vinegar, by com- 

 municating heat to the vinegar 

 carries it off in vapour, and passes 

 with it through the case contain- 

 ing the sheets of lead, which, of 

 course, areexposed to the action of 

 acetous acid, of carbonic acid from 

 the combustion of the charcoal, 

 and of oxygen and azote, or at- 

 mospheric air which has escaped 

 the action of the fuel, and which 

 may be augmented at pleasure by 

 leaving holes towards the middle 

 of the chimney to admit fresh at- 

 mospheric air. Thus are combined 

 all the circumstances necessary to 

 the production of carbonate of lead 

 — oxygen, carbonic acid, vinegar, 

 and heat. 



