WATER—ITS IMPURITIES.

ii

Nitrogen and oxygen, in varying proportions, are found in all waters.By far the greater number of the substances here mentioned occur, how-ever, in very minute quantities, or are met with only under special conditions,as in the case of free sulphuric or hydrochloric acid, which is found in onlya few cases, as in volcanic regions. Such metals as copper, zinc, lead, andothers occur only in water pumped up from mines, or in isolated cases wheresmall rivulets or springs happen to pass through lodes of metallic ore. Thesaying of Hippocrates concerning water—“ Such as the soils are, so are thewaters which run through them ”—the result of patient and shrewd observa-tion, is as true now as it was nearly twenty-live centuries ago. Water, as ageneral solvent, aided, moreover, by the mechanical effedt of its motion, iscapable of keeping not only in solution but also in suspension a large quan-tity of substances, among which organic matter holds a prominent place.

The mineral substances most frequently found in river, spring, and wellwater are as follows:—

Lime, combined with carbonic acid, mechanically suspended as chalk, orheld in solution by an excess of carbonic acid or with other acids.

Magnesia occurs as carbonate of magnesia kept in solution in carbonicacid, and also as sulphate and chloride of magnesium.

Potash and Soda are never absent from natural waters, they are mostfrequently combined with chlorine, but also with sulphuric acid ; in some,especially mineral waters so-called, they occur not unfrequently as carbonates.

Iron occurs in natural waters (mineral waters excepted) in only very smallquantities, and generally as carbonate of the protoxide held in solution bycarbonic acid ; it is, however, by no means a rare constituent, as sulphate ofthe protoxide, in water discharged from mines and coal pits. When thiswater gets into rivers it is always precipitated by the constantly presentalkaline substances in, one may say, all river waters.

Arsenious and Arsenic Acid have been detedted in many of the naturalwaters of France and at baths in Germany in appreciable quantity; the lattervery rarely, the former more frequently than is commonly supposed; thesewaters are used daily by a large number of the inhabitants of those countries,but without producing any apparently bad effedt upon their health.

With the exception of organic matter, those substances in water whichchiefly concern the dyer are lime, iron, and magnesia; the restare of littleimportance. Lime occurs in water chiefly as carbonate and sulphate ; whenit is present as carbonate it is held in solution by carbonic acid, and as thatgas is driven off when water is boiled it will of course become turbid, even if itsoriginal bulk, which should be measured previous to ebullition, be kept up asit should be by the addition of distilled water. Another and a better methodof preventing the water losing bulk whilst boiling is to condudt the operationin a flask to which a long tube is attached, so that the steam may be condensedand caused to run back into the flask.

The ebullition should be kept up for some length of time, varying according tothe quantity of water, but for not less than an hour, and the water will then beseen to become more or less turbid in proportion to the quantity of carbonateof lime contained in it. It may be easily rendered clear again by adding afew drops of hydrochloric or acetic acid, which dissolve the carbonate of limewith effervescence.