VOL. XC.l PHILOSOPHICAL TRANSACTIONS. 653 



tation may then be explained, as it is well known that mercury easily parts with 

 caloric, and requires a temperature of 600 degrees of Fahrenheit, to be main- 

 tained in the vaporous state. That the mercury is really converted into vapour, 

 by ignition of the powder, may be inferred from the thin coat of divided quick- 

 silver, which, after the explosion in the glass globe, covered its interior surface; 

 and also from the quicksilver with which a tallow candle, or a piece of gold, may 

 be evenly coated, by being held at a small distance from the inflamed powder. 

 These facts certainly render it more than probable, though they do not demon- 

 strate, that the mercury is volatilized ; because it is not unlikely that many mer- 

 curial particles are mechanically impelled against the surface of the glass, the gold, 

 and the tallow. 



As to the force of dilated mercury, Mr. Baume relates a remarkable instance of 

 it, as follows. " Un alchymiste se presenta a Mr. GeoiTroy, et l'assura qu'il 

 avoit trouve le moyen de fixer le mercure par une operation fort simple. II fit con- 

 struire six boltes rondes en fer fort epais, qui entroient les imes dans les autres ; 

 la derniere etoit assujettie par deux cercles de fer qui se croisoient en angles droits. 

 On avoit mis quelques livres de mercure dans la capacite de la premiere : on mit 

 cet appareil dans un fourneau assez rempli de charbon pour faire rougir a blanc les 

 boites de fer; mais, lorsque la chaleur eut penetre suffisamment le mercure, les 

 boites creverent, avec une telle explosion qu'il se fit un bruit epouvantable : des 

 morceaux de boites furent lances avec tant de rapidite, qu'il y en eut qui passerent 

 au travers de deux planchers ; d'autres firent sur la muraille des effets semblables 

 a ceux des eclats de bombes."* Had the alchemist proposed to fix water by the 

 same apparatus, the nest of boxes must, I suppose, have likewise been ruptured; 

 yet it does not follow that the explosion would have been so tremendous ; indeed it 

 is probable that it would not, for if, as Mr. Kirwan remarked to me, substances 

 which have the greatest specific gravity, have likewise the greatest attraction of 

 cohesion, the supposition that the vapour of mercury exceeds in expansive force 

 the vapour of water, would agree with a position of Sir Isaac Newton, that those 

 particles recede from each other with the greatest force, and are most difficultly 

 brought together, which on contact cohere most strongly. -J- 



§ g. Before attempting to investigate the constituent principles of this powder, 

 it will be proper to describe the process and manipulations which, from frequent 

 trials, seem to me best calculated to produce it. 100 gr., or a greater proportional 

 quantity, of quicksilver, not exceeding 500 gr.,^ are to be dissolved, with heat, 

 in a measured ounce and a half of nitric acid. § This solution being poured cold on 

 2 measured oz. of alcohol, 1 1 previously introduced into any convenient glass vessel, 

 a moderate heat is to be applied till an effervescence is excited. A white fume then 



* Chymie experimentale et raisonnee, torn. 2, p. 393. Paris, 8°, 1773. f Newton's Optics, p. 

 372, 4th ed. Lond. 1730. % The reason of this limitation is not on account of any danger attending 



the process ; but because the quantities of nitric acid and alcohol required for more than 500 gr., would 

 ; excite a degree of heat detrimental to the preparation. § Of the specific gravity of about 1.3. 

 || Of the specific gravity of about .849. — Orig. 



