the 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



APRIL 1844.. 



XXXVII. On the Manner in which Cotton unites with Co- 

 louring Matter. By Walter Crum, Esq., Vice-President 

 of the Philosophical Society of Glasgow*. 



THE effect of porous bodies in producing combination and 

 decomposition, independently of chemical affinity, has of 

 late years occupied considerable attention. 



If we examine, says Prof. Mitscherlich, a piece of box- wood 

 by the microscope, we find it composed of cells which have a 

 diameter of about 2T0 iT tn °f an mc h. Heated to redness, the 

 form of these cells suffers no change, for the particles of which 

 it is composed have no tendency to run together in fusion. A 

 cubic inch of box-wood charcoal boiled for some time in water 

 absorbed five-eighths of its volume of that liquid ; from which, 

 and other data, it was computed that the surface of its pores 

 was 73 square feet. 



Saussure observed that a cubic inch of box-wood charcoal 

 absorbed 35 cubic inches of carbonic acid ; and as the solid 

 part of the charcoal formed three-eighths of its bulk, these 

 35 inches of gas must ^ave been condensed into five-eighths 

 of an inch, or 56 cubic inches into one, under the ordinary 

 pressure of the atmosphere. But carbonic acid liquefies under 

 a pressure of 36 - 7 atmospheres, and therefore with a power 

 of condensation equal to 56 atmospheres, which the charcoal 

 exerted in Saussure's experiment, at least one-third of the gas 

 must have assumed the liquid state within its pores. 



Every other porous body has the same property as charcoal. 

 Raw silk, linen, thread, the dried woods of hazel and mulberry, 

 though they condense but a small quantity of carbonic acid, 

 take up from 70 to 100 times their bulk of ammoniacal gas; 



* Read before the Philosophical Society of Glasgow, February 1, 1843; 

 and communicated to this Journal by the Author. 



Phil. Mag. S. 3. Vol. 24-. No. 1 59. April 1 844. R 



