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Chemical Observations. By Thomas Graham, A.M., F.R.S.E., 

 Lecturer on Chemistry, Glasgow. 



1. On the Application of spongy Platinum to 

 eudiometry. 

 In explaining the action of cold spongy platinum in disposing 

 the union of mixed oxygen and hydrogen gases, it seems 

 necessary to suppose that hydrogen is really accendible at com- 

 mon temperatures, but that its point of accension is unna- 

 turally elevated in ordinary circumstances when it is not in 

 contact with highly-divided matter, just as the boiling point 

 of water and other liquids is elevated in smooth glass vessels. 

 This view may be correct, although it only shifts the difficulty ; 

 for we have still to explain why hydrogen, if so accendible, 

 does not take fire at superior temperatures when out of con- 

 tact with minutely divided matter. But there is an apparent 

 analogy between the circumstances of the suspension of the 

 combustion in the one case, and of the ebullition in the 

 other, on which the mind can rest with some satisfaction. 



Soon after the discovery of Dobereiner, it occurred to both 

 Dr. Henry and Dr. Turner to apply the principle to the analysis 

 of mixed gases. But they immediately found that hydrogen 

 could not at all times be withdrawn from a gaseous mixture by 

 the action of spongy platinum, although the required addition 

 of oxygen was made, as the action of that substance was 

 paralysed or entirely suspended by the presence of certain 

 gases in the mixture. The following table of Dr. Henry's 

 exhibits the sum of our information on this subject. 



11 The first column exhibits the number of volumes of each 

 gas required to render one volume of an explosive mixture of 

 hydrogen and oxygen (in the usual proportion of two hydro- 

 gen to one oxygen) uninflammable by the discharge of a 

 Leyden jar; while the second column shews the number of 

 volumes of each gas necessary, in some cases, to render one 

 volume of an explosive mixture insensible to the action of the 

 sponge, and in other cases indicates the number which may 

 be added without preventing immediate combination. 



" In the first column, the numbers marked with an asterisk 

 were determined by Sir H. Davy : the remaining numbers in 



