Intelligence and Miscellaneous Articles. 75 



throw any light on the existence or structure of the supposed glan- 

 dular follicle noticed by Blumenbach. 



Mr. Woods concluded his communication by remarking, that it is 

 difficult to conjecture for what purpose these minute claws are deve- 

 loped in so strange a situation, that of stimulating the animals to 

 anger being of course out of the question. It is at least evident, he 

 observes, that they can fulfil no very important design in the animal 

 ceconomy, from their smallness, their variable form, their complete 

 envelopement in the fur, and especially from the readiness with which 

 they are detached and consequently the majority of individuals de- 

 prived of them for the remainder of their lives. 



XV. Intelligence and Miscellaneous Articles. 



ACTION OF SULPHUROUS ACID ON THE PERSALTS OF IRON. 



IT is well known that sulphurous acid when added to the solutions 

 of those metals which possess a weak affinity for oxygen, such as 

 platinum, gold and mercury, precipitates them in the metallic form. 



I find it stated also in the last (fourth) edition of Dr. Turner's 

 excellent work, the Elements of Chemistry (p. 274), that when sul- 

 phurous acid is mixed with peroxide of iron in solution, it deprives 

 that compound of part of its oxygen, and converts it into protoxide. 



This is an effect which it would be natural to anticipate ; and yet 

 I apprehend that such is not the case ; for when a solution of sul- 

 phurous acid is added to one of persulphate of iron, the colour of the 

 solution, instead of being changedfrom red or reddish yellow toblueish 

 green, becomes a very deep red ; and I have found that if a grain of 

 protosulphate of iron be converted by nitric acid into persulphate, 

 its presence in a pint of water may be detected by adding sulphu- 

 rous acid, the solution becoming slightly yellowish *. When the 

 solution of persulphate of iron is moderately strong, the intensity of 

 the colour is so much increased by sulphurous acid, as to resemble 

 the effect produced by sulphocyanic acid ; so that I think it ex- 

 tremely probable that what has been caused by the former may 

 have been attributed to the latter. It is however to be observed, 

 that the colouring effect produced by the sulphurous acid disappears 

 in a few hours, which is not the case with that derived from sulpho- 

 cyanic acid. R. P. 



IMPROVEMENT IN THE QUALITY OF IRON AND STEEL, FROM 

 THEIR BECOMING RUSTY WHEN BURIED IN THE EARTH. 



The following "extract from the Chronicles of Old London Bridge," 

 is sufficiently curious in itself to merit insertion in the Philosophical 



* The red colour of the solution is presumptive evidence that the per- 

 oxide of iron is not reduced to the state of protoxide by the sulphurous 

 acid ; and this conclusion is strengthened by considering the action of fer- 

 rocyanate of potash, which gives prussian blue, even when the sulphurous 

 acid is greatly in excess, and after the red colour which it had produced ha& 

 disappeared. 



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