Krug von Nidda on the Mineral Springs of Iceland. 105 

 According to Black* 



........ 0.51 



Sulphate of soda, ..... 1.28 



Muriate of soda, , 2.90 



Silica, ........ 3.73 



Alumina, ....... 0.05 



8.47 



The water of the Geyser was examined by Black only ; it 

 contains in 10,000 parts, 



10.75 



The most important discrepancy between the analyses of the 

 two chemists is, that Black found in both springs a considerable 

 quantity of caustic soda ; whereas, according to Klaproth, the 

 soda is combined with carbonic acid. 



I was unfortunately prevented from bringing with me water 

 from the springs in order to have it submitted to chemical ana- 

 lysis, and I am therefore unable to decide which of the two che- 

 mists is correct ; nor can it be determined whether, as Klaproth 

 imagined, Black merely supposed that the soda existed in a 

 caustic state from having assumed that the silica in the springs 

 was chemically combined with the sods. 



Barrow sent a small quantity of the Geyser water to Mr Fara- 

 day, who examined it with a view to determine the nature of its 

 contents. Faraday, in a letter to Barrow, says, that the water is 

 characterized by containing a peculiar combination of silica and 

 soda : this combination ceases to exist when the water is evaporat- 

 ed, and the silica is then deposited in an insoluble condition; while 

 the alkali, probably by the agency of the carbonic acid of the 

 atmosphere, is set free, and remains dissolved in the water in 



Transactions of the Royal Society of Edinburgh for the year 1789, 

 vol. iii. 

 t Barrow's Visit to Iceland, p. 209-211. 



