One Thousand Experiments, S;c. 3G1 



a dozen to twenty pounds." So 'practical a chemist as Mr. Colia 

 Mackenzie ought to know that mercury is the very substance 

 employed to absorb chlorine in analytical researches on mixed 

 gases ; and that no practical chemist of common sense, ever 

 tried to receive chlorine over mercury. 



*' Exp. 47 1 . Iodine vapour. Put a small quantity of iodine 

 into a retort, and hold it over a lamp ; when heated considera- 

 bly (about 300°) a very beautiful vapour, or gas, will come over, 

 ■which may" be received in jars on the pneumatic shelf, over 

 water." Quere ; is Mr. Mackenzie's water also heated to 300°; 

 did he ever see, or hear, of iodine as a beautiful gas standing 

 over water in the pneumatic trough ? 



" Combustion is the decomposition of a body at an elevated 

 temperature, with the evolution of light and heat. Some sup- 

 pose combustion to be the effect of a certain degree of motion 

 of the particles of combustible bodies ; and that flame is merely 

 a transparency, or luminosity, of these particles when they are 

 thrown to certain distances with considerable velocity*." One 

 can hardly afford to waste criticism on such pompous nonsense. 

 Combustion is known to be most vivid, when simple bodies are 

 engaged ; and when there is no decomposition, but the reverse, 

 as with phosphorus and oxygen, sulphur and copper, Sfc. 



" Exp. 529. Combustibility of hydrozincic gas." This fine 

 name merely signifies hydrogen procured by acting on zinc, as 

 usual, with a dilute acid. 



" Exp. 545. Tin burns brilliantly in oxygen gas. Heat some 

 granulated tin considerably, in a platinum spoon, and in this 

 state immeise it in oxygen gas ; a \ery beautiful combustion, 

 attended by a brilliant white light will instantly take place; 

 when oxide of tin will be formed." The possessor of such a 

 spoon had better not try this trick, for if the tin burns, which 

 we have some doubts about, the spoon would melt, thus adding 

 to the instructii'cncss of our author's experiment. 



" Exp. 571. A lighted taper burns with ?nuch energy in 

 chlorine gas." It so happens that it is presently extinguished. 



" Exp. 572. Combustion of charco(dpoivder in chlorine. Pour 

 some dry charcoal, newly made and finely powdered, into ajar, 

 containing chlorine gas ; a very beautiful combustion will take 

 place, displaying a stream of fire." Not true. 



" Exj). 719. Latent heat is necessary to preserve bodies in 

 the so//V/, liquid, and gaseous states." Dr. Black imagined that 

 bodies wotdd keep very well in tin; solid state, without the help 

 of latent heat. Mr. Mackenzie has discovered that they will 

 not. 



" When bodies are mixed or combined, and the density or 

 bulk becomes less than that of the fluids before mixture, heat 



• Page CHI. 

 Vol.. XII. 2 B 



