266* HYDROGEN. 



ration, is not removed by filtering. Animal charcoal is the 

 proper substance for discolouring liquid s, as it withdraws 

 organic colouring matter, even when in a state of solution. 



In the process of clarifying liquors, by dissolving in them the 

 white of egg and other albuminous fluids, the temperature is 

 raised so as to coagulate the albumen, which thus forms a 

 delicate net-work throughout the liquid, and is afterwards 

 thrown up as scum in the boiling, carrying all the foreign matter 

 suspended in the liquid along with it. 



The most usual earthy impurities in water, occasioning its 

 hardness, are sulphate of lime, and the carbonate of lime dissolved 

 in carbonic acid, both of which are precipitated on boiling 

 the water, and occasion an earthy incrustation of the boiler. 

 When waters contain iron, they are termed chalybeate; this 

 metal is most frequently in the state of carbonate dissolved in 

 carbonic acid, and rarely in a proportion exceeding one grain in 

 a pound of water. The -sulphureous waters, which are recog- 

 nized by their peculiar odour, and by blackening silver and salts 

 of lead, contain sulphuretted hydrogen gas, in a proportion not 

 exceeding the usual proportion of air in spring water, and no 

 oxygen. Saline waters, for the most part contain various salts 

 of lime and magnesia, and generally common salt. Their den- 

 sity is always considerably higher than that of pure water. 

 Sea-water contains 3J per cent, of saline matter, and has a 

 density 1.0274. Its composition is interesting, as the sea 

 comes to be the grand depository of all the soluble matter of the 

 globe. A most minute and valuable analysis of the water of the 

 English Channel has lately been executed by Dr. Schweitzer of 

 Brighton, the particulars of which I subjoin in contrast with an 

 analysis of the water of the Mediterranean by M. Laurens : 



Sea-water of the English Channel. Of the Mediterranean. 



Grains. Grains. 



Water . . . 964.743/2 . . . 959.26 



Chloride of sodium . 27.05948 . . . 27.22 



potassium. 0.76552 . . . 0.01 



magnesium 3.66658 . . . 6.14 



Bromide of magnesium 0.02929 



Sulphate of magnesia . 2.29578 . . . 7.02 



lime . . 1.40662 . . . 0.15 



Carbonate of lime . 0.03301 Garb, of lime & magn. 0.20 



1000.0000 1000.00 



