Metallic Compounds of Chlorine, Bromine, and Iodine. 399 



justed, that the mean point between the Initial and final temperatures was from 

 half a degree to one degree above that of the air, the entire correction required 

 was in all cases very small. 



13. The value in water of the different parts of the apparatus was estimated 

 with as much precision as possible. The specific heat of the copper and brass of 

 the copper vessel was assumed to be 0.095, that of the glass of the glass vessel 

 and balls was determined by a careful experiment to be 0.140. The leather, cork, 

 and cement were found to be nearly equivalent to 1.1 gr. of water, and the spe- 

 cific heat of the solution formed in each experiment was also determined. 



14. In the description of the experiments I have used the following abbre- 

 viations : 



Bar. — The height of the barometer. 



Th. air. — The temperature of the air. 



T'. — The initial temperature of the water in the copper vessel. 



T'. — The final temperature of the same. 



Inc. c. — The increment of temperature corrected for heating and cooling, 

 according to the formulas given before. 



Aq. — The weight of the water in the copper vessel. 



Sn. — The weight of water equivalent to the solution of the compound formed. 

 This is found by multiplying the absolute weight of the solution by its specific 

 heat, which is also given. 



Vss. — The weight of water equivalent to the vessels and other solid substances 

 used in each experiment. 



15. The temperatures are given in the degrees of Fahrenheit's scale ; the 

 height of the barometer in English inches ; the volume of the chlorine in cubic 

 centimetres ; and the weight of the water, &c. in grammes. The volume of the 

 chlorine gas requires to be corrected for moisture, as well as for temperature and 

 pressure, and I have assumed the weight of 100 cubic centimetres of the dry gas 

 at 32°, and under a pressure of 29.92 in. to be 0.317 grammes. 



COMPOUNDS OF ZINC. 



16. Zinc and chlorine, Zn + CI -|- Aq. 



Bar 29.47 in. . . 29.07 in. . . 29.97 in. 



Th.air 50°.70 . . . 48°.50 . . . SO^.SO 



