508 Mr. T. Tate's Experimental Researches on the 



The following experiment was made to determine how far the 

 law of diffusion is affected by direct chemical action. 



Experiment XIII. 



The absorbent used in this "experiment was unsized paper 

 saturated with a solution of 8 per cent, of carbonate of potassa 

 and then carefully dried, so that the paper was uniformly impreg- 

 nated with the salt. The liquid was diluted sulphuric acid having 

 a specific gravity of 1013. 



Hence it appears that the general formula, expressing the rate 

 of diffusion, holds true in cases where there is a known decided 

 chemical action. It would seem that the ascent of the liquid 

 through the pores of an absorbent is in most cases attended by 

 chemical action. 



The diluted acid used in this experiment was found to have 

 the same diffusibility as distilled water, the formula of diffusion 

 being T = 3*5 S 2 at mean temperature. The slow rate of diffu- 

 sion of the diluted sulphuric acid in this experiment is not a 

 little remarkable. In most cases direct chemical action tends to 

 accelerate the diffusion. 



The following experiment was made to determine the amount 

 of heat evolved by the process of absorption. 



Experiment XIV. 



The bulb of a thermometer was infolded with dry unsized 

 paper, which extended about one inch below the bulb. The 

 extremity of the paper was brought in contact with water placed 

 in a small-mouthed bottle. The temperature of the water was 

 the same as that of the air, viz. 56°. As the liquid ascended 

 through the pores of the absorbent, the temperature, indicated 

 by the thermometer, gradually rose until it reached 61°, giving 

 a maximum rise of 5° due to the heat evolved by absorption. 



The naked bulb of a thermometer was inserted in some dry 

 plasterof paris placed in an evaporating dish. A sufficient quantity 

 of water, having the same temperature as the air, viz 56°, was 

 then poured into the dish; after the higher portion of the 

 plaster of paris had become wet by absorption, the temperature, 



