444 APPENDIX. 



combining measure of hydrogen, chlorine, etc., becomes 

 2, as a consequence, and that of other gases or vapors is 

 proportionally changed. In the production of compound 

 gases, the elements either suffer no condensation or experi- 

 ence a very simple change of volume. Thus hydrochloric 

 acid gas, formed by the combustion of hydrogen and chlo- 

 rine, possesses the united volumes of its constituents. 



EQUIVALENT VOLUMES OF COMPOUND GASES. As the 

 equivalent, or combining proportion of a compound, is 

 equal to the sum of the equivalents of its constituents, it 

 follows that the combining measure of hydrochloric acid, 

 is equal to the sum of the combining measures of hydro- 

 gen and chlorine, 2+2 = 4. Ammonia is formed by the 

 union of three volumes of hydrogen, and one of nitrogen. 

 Condensation takes place to the amount of of the whole 

 volume of their mixed gases. The combining measure is 

 therefore equal to the sum of the combining measures of the 

 constituents divided by 2. The sum of the combining 

 measures is 8. 8-7-2=4. Steam is composed of one com- 

 bining measure (two volumes) of hydrogen, united with 

 one combining measure or volume of oxygen, and condensed 

 to two volumes in combination. Its combining measure is 

 therefore 2. The above instances may serve as examples 

 of the interesting relations of atomic weights, specific quan- 

 tity, and combining measures. 



CALCULATION OP SPECIFIC GRAVITY. The density or spe- 

 cific gravity of a compound vapor or gas of known propor- 

 tional composition, may be readily calculated from that of 

 its constituents, supposing the amount of condensation which 

 takes place in their combination to be known. The results 

 thus obtained, are more accurate than any results of experi- 

 ment. In like manner the proportional composition of a 

 compound may be calculated from a knowledge of its ele- 

 ments and density. The density of the vapor of carbon and 



