350 Mixter — Determination of the Heat of Dissociation 



The results are given for gram molecules and 1 and 12 are 

 taken for the atomic weights of hydrogen and carbon respec- 

 tively. No corrections are made for water vapor or nitric acid 

 remaining after explosion, as these would only change the sixth 

 figure of the results. 



Acetylene. 



The acetylene gas was made by thrusting lumps of calcium 

 carbide into water in a glass gas holder. By means of ferrous 

 hydroxide it was freed from traces of oxygen. Thus prepared 

 the gas contained from 1 to 3 per cent of nitrogen. It was 

 dried before pumping into the bomb by passing it through a 

 kilo of small sticks of potassium hydroxide. The oxygen used 

 was made from chlorate and was kept over water containing a 

 little sodium hydroxide. 



Experiment 1. — Acetylene, 7*24 grams, gave too great a rise 

 of temperature to be measured by the differential thermom- 

 eter. Accordingly the thermometer graduated to tenths of a 

 degree was used in the calorimeter. The result was 51,900 

 calories for 26 grams of acetylene. 



Experiment 2. — Acetylene, 5488 grams; temperature of 

 jacket 2*7° by the differential thermometer used in the calori- 

 meter. The residual gas was free from acetylene. 



Minutes. Temperature. 



Water in calorimeter, 3000 grams. 

 Water equivalent of 



calorimeter, 250 " 







0-285 



3 



0-290 



6 



0-295 



9 



3-740 



12 



3-730 



15 



3-709 



18 



3-696 



21 



3-682 



3250 

 Temperature interval, 



3-73 — 0-295 4-0-027 = 3'462 c 



Multiplying this temperature interval by 3,250 and by the 

 ratio of 26 to the mass of the substance taken we deduce for 

 26 grams of acetylene 53,300°. 



Experiment 3. — In this experiment the bomb leaked after 

 charging with acetylene. Hence it is better not to record the 

 calorimetric result although it accorded fairly with the other. 



Experiment 4>. — Acetylene, 6-493 grams ; jacket, 3*4°. The 

 residual gas did not contain acetylene. 



Water and water equivalent of 

 calorimeter, 3250 grams. 



Temperature interval, 



4-114 -0-0274-0-018 ±= 4*105° 



mutes. 



Temperature, 







o-o 



3 



o-oi 



6 



0-02 



9 



0-027 



12 



4-110 



15 



4114 



