the Substances usually present in Water. 45 



plete. After these have been heated to redness, neutral phosphate 

 of magnesia remains, from which is known the quantity of magnesiat. 



Any sulphuric acid in the remaining fluid, together with the ex- 

 cess of phosphoric, is now removed by acetate of lead, and, after 

 this precipitate is separated, the excess of lead is thrown down by car- 

 bonate of ammonia. There is now left in solution only chlorides of 

 potassium and sodium, and easily volatilizable salts of ammonia. 

 This solution is evaporated to dryness, ignited, and these chlorides 

 weighed. 



They are re- dissolved, and any charcoal from organic matters is 

 separated, and its weight deducted from theirs. A solution of chlo- 

 ride of platinum is added, the whole is evaporated to dryness, and 

 as much is re- dissolved as will dissolve in a little cold water ; chloride 

 of potassium and platinum remains, from which is gained a know- 

 ledge of the quantity of potass. The quantity of chloride of potassi- 

 um in it is also calculated, and this, deducted from that of the mixed 

 chlorides, gives that of the chloride of sodium ; hence that of the 

 soda is derived. If it be wished to exhibit the chloride of sodium 

 apart, it may be done by separating the excess of platinum in the 

 last solution by carbonate of ammonia, evaporation to dryness, and 

 ignition. 



The chemical examination of waters is of immense con- 

 sequence, not so much in reference to what are properly 

 called mineral springs, as in regard to that water employed 

 in the ordinary purposes of life. The presence of a little 

 animal or vegetable matter, of nitrates, or of a minute portion 

 of some other ingredient, may, by the continued use of such 

 water for months or years, give rise to diseases in a great 

 measure constituting the difference between a healthy and un- 

 healthy locality. It is also of great consequence in the arts 

 and manufactures, such as brewing, distilling, sugar refining, 

 bleaching, and particularly in dyeing. A celebrated dyer of a 

 beautiful red in France, could not succeed on removing his 

 residence to another place. He investigated the cause, it lay 

 in the water, and, on imitating artificially the water at his 

 former residence, his colour became as bright as before. 



