40 Dr. Thomsons Experiments on the heat or cold 



66. Bignonia 4:-locularis. Common in the jungles, and 

 somewhat resembling the ash. The white flowers rising 

 from the ends of the branches look showy at a distance, 

 but cannot bear inspection. 



57. Bignonia spathacea, 



58. Bignonia radicans. I have only found these two in 

 gardens; both have pretty flowers, particularly the latter; 

 it is a shrub of very slow growth, and was brought from 

 China, I believe. 



(To he continued.) 



Article VI. 



Experiments on the heat or cold produced hy dissolving salts in 

 water. By Thomas Thomson, M. D., F. R. S. L. & E., 

 &c., Regius Professor of Chemistry in the University of 

 Glasgow. 



1. 300 grains of crystallized carbonate of soda in powder, 

 were thrown into 1000 grains of water of the temperature 

 59° in a tumbler, and the mixture was stirred till the salt 

 was dissolved ; the thermometer sunk to 43° or 16 degrees. 



The water of crystallization in 300 grains of carbonate of 

 soda is 187| grains ; which is \ of 1300 grains, the whole of 

 the liquid and salt included. Now, the water of crystalliza- 

 tion becoming liquid would absorb 140° of heat. Hence 

 the temperature ought to have sunk ^ of 140 or 20°. But 

 the fall was only 16°; the difference is owing to the quan- 

 tity of heat given out by the glass tumbler, which of course 

 would prevent the temperature from sinking so low as it 

 otherwise would have done. 



300 grains of anhydrous carbonate of soda in powder, 

 were thrown into 1000 grains of water of the temperature 

 57°*5, and stirred with a thermometer till the temperature 

 ceased to rise. The thermometer rose from 57°* 5 to 79°'5 

 or 22°. In another experiment from 61° to 82°-5 or 2r-5. 

 There remained undissolved 7*7 grains of salt. The water 

 of crystallization seems to be absorbed by this salt in the first 

 place ; hence the reason of the rise of temperature. This 

 water amounts to 182 J grains or about \ of the salt and 

 water. Hence, the rise of temperature should be ^ of 140 

 or 20°. It exceeds this quantity a very little ; the reason 



