Laws of Absorption of Liquids by Porous Substances. 507 



Diffusibility sol. No. 1 =740= -74 x -6°. 



„ „ No. 2 = *447 = *74x *6 very nearly. 



„ „ No. 3 = -262 = -74 x -6 s very nearly. 



Here it will be seen that the numbers expressing the diffusi- 

 bility of the different solutions are very nearly in geometrical 

 progression. 



Heuce we derive the following law : — If the per -cent age of 

 starch contained in three different solutions be expressed by an 

 ascending geometrical progression, the diffusibility of the solutions 

 will be expressed by a descending geometrical progression. 



The results of the following experiment are confirmatory of 

 this law. 



Experiment XII. 



In this experiment the liquids used were six different solu- 

 tions of carbonate of potassa, containing respectively £, J, 1, 2, 4, 

 and 8 per cent, of the salt ; that is, the weights of salt dissolved 

 in equal parts of distilled water were as the numbers in the geo- 

 metrical progression J, -J, I, 2, 4, and 8. The absorbent used 

 was unsized paper. 



The results of the experiment gave the following formulae of 

 ascent of the different liquids : — 



Formulae of ascent. 

 Distilled water . . . . T=3'5S 2 

 Solution No. 1 ... . T=3-25 S 2 

 No. 2 . . . . T=3«75S 2 

 No. 3 .... T= 4S 2 

 No. 4 ... . T=4-33S 2 

 No. 5 . . . . T= 5S 2 

 No. 6 ... . T=5-33S 2 



Hence we find from equation (10), diffusibility of water being- 

 unity. 



Diffusibility sol. No. 1 = 1-038 

 „ No. 2 = 

 „ No. 3 = 



No. 4= 

 „ No. 5 = 



„ No. 6 = 



Hence it appears that the numbers expressing the diffusive- 

 ness of the different solutions are very nearly in geometrical 

 progression, thereby confirming the law enunciated in the fore- 

 going experiment. 



The diffusibility of solution No. 1 is a little greater than that 

 of pure water. A slight addition of an alkaline salt to water 

 seems to increase its diffusiveness. 



2L2 



