1822.] Scientific Intelligence. 315 



presence of chlorine, even when uncombined with hydrogen ; and it 

 is also evident, that nitrate of silver cannot be relied upon for deter- 

 mining the quantity of free chlorine : nor did Mr. Faraday and myself 

 attempt to employ it for this purpose. — Edit, 



III. Composition of Oxalic Acid. 



M. Dobereiner stated about five years since, that oxalic acid con- 

 tains no hydrogen, and that it is formed of equal volumes of oxide of 

 carbon and carbonic acid, combined with a proportion of water. He 

 considered this water as essential to its existence, and that if it were 

 taken away, the acid would be decomposed. Reflecting afterwards 

 upon the great affinity which fuming sulphuric acid has for water, he 

 performed the following experiment, which he has described in a 

 pamphlet upon pneumatic chemistry : 



Five grains of dried oxalic acid, but still containing a quantity of 

 water, were mixed with 200 grains of fuming sulphuric acid, in 

 an apparatus for receiving gases over mercury. The oxalic acid gra- 

 dually and totally disappeared, and produced 94 cubic inches of gas ; 

 the sulphuric acid became less fuming. 



The gases washed with ammonia were reduced to 'iT cubic inches, 

 and consequently contained 47 cubic inches of carbonic acid. The 

 gas which the ammonia did not absorb was oxide of carbon ; for it 

 burnt with a blue flame, and being detonated in Volta's eudiometer 

 with half its volume of oxygen, it produced an equal volume of the car- 

 bonic acid, without any appearance of water ; the weight of carbonic 

 acid, added to that of the oxide of carbon, represents exactly that of 

 the anhydrous oxalic acid ; and M. Dobereiner concludes that this acid 

 contains no hydrogen ; for if it contained any, sulphurous acid should 

 be formed ; or if the hydrogen was combined with a portion of oxygen 

 of the oxalic acid, the carbonic gas and the oxide of carbon would 

 Ije found in different proportions. 



In this experiment, the sulphuric acid combines only with the 

 water, and in order that it may succeed, it is requisite that the sul- 

 phuric acid should be fuming, like that of Nordhaussen : for common 

 acid does not decompose oxalic acid. — (Ann. de Chimie et Phys.) 



IV. Hot Springs of St. Michael. 



The vicinity of the springs is indicated by the increased temper- 

 ature of the earth, a sulphurous odour, and the escape of vapour or 

 steam from every crack or fissure in the ground. The volumes of 

 smoke and steam rolling upwards from the surface to a great height, 

 till they are gradually diffused through the atmosphere, or mingle 

 with the heavier clouds that crown the summit of the mountains, 

 produce a striking effect. The confused rumbling and hissing noise 

 that is heard for some time before we arrive in sight of the springs, 

 increases at last to an incessant and terrific roar, and seems to issua 

 from the very spot on which we stand. The earth returns a hollow 

 sound, and great caution is required to avoid stepping into the pools 

 and streams of boiling water with which its surface is covered. 



The quantity of hot water discharged through the innumerable 

 orifices in the ground is prodigiously great, and the different streams 

 unite, forming a small river, that, still hot, joins the Ribeira Quente. 

 The largest streams are termed *' caldeiras/* or boilers, and a 

 shallow basin of earthy matter has been formed round each of them 



