^STATURAL WATERS 



71 



Sodium chloride 

 Potassium chloride . 

 Magnesium chloride. 

 Magnesium bromide 

 Magnesium sulphate 

 Magnesium carbonate 

 Magnesium nitrate . 

 Calcium sulphate . 

 Calcium carbonate . 

 Ammonium chloride 

 Ferrous carbonate . 

 Silicic acid 



33-859 

 In certain lakes having no communication with the ocean 

 the concentration of the water becomes much greater, and the 

 total solid matter may reach seven or eight times that found 

 in the ocean. Examples of such waters are found in the Dead 

 Sea and the Great Salt Lake of Utah. 



Relations of Water to Heat.— The physical properties of 

 water, especially in its relations towards heat, are remarkable 

 in many ways, and of the utmost importance. It is therefore 

 desirable that the student should be familiar with these pro- 

 perties, in order that he may realise the parts played by water 

 in nature. 



Pure water is usually described as colourless, but careful 

 examination will show that when seen in sufficiently thick 

 layers it has a bluish -green colour. It is a bad conductor of 

 heat — i.e., heat travels sloAvly from one particle of water to 

 another — but usually a mass of water is warmed readily, espe- 

 cially if the source of heat be below. In this case the distri- 

 bution of heat is effected by a process distinct from conduction, 

 known as convection. The particles of water nearest the source 

 of heat become warmed, expand, and consequently rise, the 

 cooler, and therefore heavier, particles above or around them 

 taking their place. A circulation is thus set up, the warmer 

 water continually rising and the colder sinking. 



Specific Heat. — Water has a high specific heat. By this is 

 meant that to raise the temperature of a given mass of water 



