Metallic Compounds of Chlorine, Bromine, and Iodine. 397 



filled with the gas in a moist state, and two very flimsy glass balls, such as those 

 shown in fig. 4, were afterwards cautiously introduced. One of these balls con- 

 tained a large excess of the metal in the state of fine filings ; the other, a quantity 

 of water, whose weight had been adjusted nearly in the proportions before de- 

 scribed. On the other hand, when bromine and iodine were under examination, 

 the metal and water were introduced into the vessel itself, while the bromine, or 

 iodine, carefully weighed, was contained in one of the little balls. The vessel 

 was in all cases closed by a good cork, which was rendered air-tight by cement. 

 A small stud of iron wire was inserted into the cork to maintain the glass vessel 

 in its proper position in the interior of the apparatus. This vessel, thus prepared, 

 was agitated for some time in water adjusted to the proper temperature, and then 

 placed in the light copper vessel, fig. 2, which was immediately filled with water, 

 and its lid screwed on. In the top and bottom of the copper vessel, loops of cop- 

 per wire were inserted, by means of which it could be suspended, without contact 

 of the hand, in the centre of a cylindrical vessel of tin plate, fig. 3, having a de- 

 tached cover above and below. The complete arrangement will be readily un- 

 derstood from an inspection of fig. 5. In the lids of the tin cylinder and copper 

 vessel corresponding apertures existed, through which the bulb of a delicate ther- 

 mometer could be introduced into the water in the interior of the latter. On 

 withdrawing the thermometer the aperture in the copper vessel could be closed, 

 in the course of two or three seconds, without touching the vessel itself. By this 

 arrangement the copper vessel with its contents was suspended in a fixed position 

 in the centre of, but not in contact with, an outer cylinder of tin plate, while at 

 the same time the temperature of the water could be noted at any time without 

 removing it from its situation. A larger cylindrical vessel, capable of being ra- 

 pidly rotated round its shorter axis, completed the whole apparatus. It is shown 

 in fig. 6. 



10. When an observation was made the copper vessel was suspended in the 

 cylinder, the opening in its lid closed, and the apparatus placed in a horizontal 

 position, and then cautiously agitated (lest the glass balls should break), till a 

 perfectly uniform temperature was established through the whole of the copper 

 vessel and its contents. This being accomplished, the cylinder was again placed 

 in the position represented in fig. 5, the temperature of the water carefully 

 noted, and the cork replaced. It was then suddenly shaken, so as to rupture the 



