Part 22

The water from this well is perfectly bright, clear, and even brilliant; it has an agreeable soft taste, and is much esteemed by the inhabitants of the parish, although, as will be seen by the subjoined analysis, it is an exceedingly hard water, and the large quantity of earthy salts it contains renders it unfit for all culinary and for most domestic purposes.

When heated to the boiling point, this water becomes turbid, and by continued boiling of an imperial gallon of the water for two hours, 23·03 grs. of solid matter were deposited, consisting of 22·15 grs. carbonate of lime, and 0·88 carbonate of magnesia, with a trace of phosphate of lime.

An imperial gallon of this water, when evaporated to dryness and the residue dried at a temperature of about 300° Fahr., left a residue which amounted to 88·07 grs. From another sample of the same water taken a month afterwards, 84·53 grs. of solid residue were obtained.

By an analysis, an imperial gallon of the water gave--

Carbonate of lime 28·97 Carbonate of magnesia 2·61 Sulphate of lime 17·85 Chloride of sodium 16·95 Nitrate of potass 12·40 Nitrate of soda 1·50 Nitrate of magnesia 4·92 Nitrate of ammonia 4·01 Silica 0·80 Phosphate of lime traces Organic matter ------ 90·01

The residue left by evaporation was of a light brown colour; when calcined at a low red heat it became slightly charred; but I could not, with any degree of certainty, determine the precise quantity of organic matter it contained: it was certainly very small.

The excess of solid matter, as shown by the analysis, over the quantity obtained by evaporating the water to dryness, is owing to the decomposition of the nitrate of ammonia.

The quantity of alkaline and earthy nitrates in this water is very remarkable. These salts are doubtless derived from the decomposition of animal matter in the adjacent churchyard. Their presence, conjoined with the inconsiderable quantity of organic matter which the water contains, illustrates in a very forcible manner the power the earth possesses of depriving the water that percolates it of any animal matter it may hold in solution; and moreover shows in how complete and rapid a manner this process is effected.

In this case the distance of the well from the churchyard is little more than the breadth of the footpath, and yet this short extent of intervening ground has, by virtue of the oxidizing power of the earth, been sufficient wholly to decompose and render inoffensive the liquid animal matter that has oozed from the putrefying corpses in the churchyard.

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The result of these analyses confirms the general statement that the water derived from the sandy districts of Farnham and Bagshot is of eminent purity, and therefore peculiarly fitted for all those purposes of domestic and manufacturing economy which require the use of a very soft water.

When regarded in conjunction with the analyses made by other chemists, of the water taken from the streams, pools, and other collections of water in the same locality, it also points out that, if it be desirable to secure the water in its utmost state of purity, it should be collected at its very source, before it has had time to become impregnated with the various mineral and saline ingredients of the different soils through which it would have to pass. The total absence of free carbonic acid in these waters is a very remarkable fact, and one which I believe has not been hitherto noticed.

It will also be perceived that the principal solid constituent of the water supplied by the New River and the East London companies is carbonate of lime, held in solution by an excess of carbonic acid, an opinion already expressed by several chemists. These waters also contain an appreciable quantity of oxide of iron.

When the water from these sources is boiled, or simply brought to the boiling temperature, the excess of carbonic acid is driven off, and the carbonate of lime being thus deprived of its solvent, the greater portion of it, together with the oxide of iron, is thrown down in the form of an insoluble crystalline powder, while the water is rendered comparatively soft and pure.

Were it therefore possible that means could be devised by which the quantity of water necessary for the daily supply of London could be deprived of its excess of earthy carbonates in a manner sufficiently economic, comprehensive, and effectual, the citizens of the metropolis would enjoy the advantage of a tolerably pure soft water, free from those inconveniences which attend the use of the present hard-water supply.

Confining myself wholly to a chemical view of the subject, the principal disadvantages attending the use of hard river waters are--

First, The precipitation of earthy matter on the inside of vessels in which the water is heated. This furring of the vessel, as it is called, leads to its more rapid destruction, and has also the inconvenience of rendering it more difficult to cleanse, so that the flavour and odour of the various substances cooked in it are not readily removed. From the non-conducting power of the earthy crust, an increased consumption of fuel is also required for the due heating of the vessel.

Secondly, The admixture of the earthy salts with the various articles of food submitted to the action of hot water.

Thirdly, Diminished solvent power, as required for the purposes of the chemist, the brewer, and for many domestic purposes, as in the making of tea, soups, &c.

Fourthly, Diminished cleansing power, both as regards the direct solvent action of the water, and also as causing the decomposition of soap, and consequent increased consumption of that article. I must, however, remark that the annual loss reported to arise from this cause appears to me considerably overrated, since water is rarely used for the washing of linen until previously boiled, and the common practice of adding carbonate of soda to the water completely destroys the ill effects resulting from the hardness of the water. The additional expense of the carbonate of soda, thus added, is too trifling to merit notice; but when this salt is used in excess, as is generally the case, it produces the more serious evil of materially impairing the strength of the fabric submitted to its action.

The only real advantage which hard water possesses over soft (and in the present state of things one of considerable importance), is, that it does not act upon or erode the lead of the pipes and cisterns in which it is contained.

There are also some particular cases of minor importance in which hard water is preferred; thus dyers prefer hard water for rinsing of their goods, soft water extracting too much of the colour; but these cases are comparatively rare, and might be easily accomplished by an artificial hardening of the water.

The following Table indicates the relative hardness of the different waters as determined by the Soap test; distilled water being taken as unity, as proposed by Professor Brande. It also shows the effect of boiling in reducing the hardness of the water. The numbers express the direct quantity of an alcoholic solution of soap, which an equal bulk of each water requires in order to form a lather remaining permanent for from five to ten minutes.

Distilled water 1·0 Water from Haslemere 2·4 Boorley 1·5 Barford 2·4 Water of the New River Company 13·3 Ditto after being boiled 4·7 Water of the East London Company 19·0 Ditto after being boiled 5·6 Water from the well in Bishopsgate-street 47·4 Ditto after being boiled 26·0

The experiments which I have recently made on the action of pure water upon lead, clearly point out the necessity of keeping the pipes always full, especially in those instances in which the water has a tendency, however slight, to erode the lead. As the importance of this part of the question does not appear to have been sufficiently appreciated by the advocates of a constant instead of an intermittent supply, I will briefly recount the facts of the case, although I do not offer them as presenting anything particularly novel. If a piece of bright lead be placed in a stoppered bottle, completely filled with recently distilled water, so that the access of air be wholly excluded, the lead is but very slightly acted upon, and it is only after the lapse of three or four days that its surface becomes spangled with a few minute crystals of carbonate of lead.

If the stopper of the bottle be now removed, the lead still remaining beneath the surface of the water, the erosive action of the water on the lead proceeds more rapidly, but still slowly. But if now a portion of the water be poured off, so as to leave the lead only partially immersed, rapid action on the lead immediately commences. In the course of thirty-six or forty-eight hours, its surface becomes coated with crystalline scales of carbonate of lead, which, falling off, are succeeded by others, so that after the lapse of a few days an abundant deposit of carbonate and hydrated oxide of lead is found at the bottom of the vessel. If the experiment be made with distilled water that has been previously agitated with air, so as to completely aërate it, the lead is more rapidly acted upon, even in a closed vessel, thus clearly showing how much the action of the water upon the lead depends upon the presence or absence of atmospheric air.

Now, in a minor degree, this is precisely what takes place in a leaden pipe conveying water capable of eroding lead. While the pipe is full, comparatively but little action occurs; but when the pipe is filled alternately with air and with water, it is placed under the most favourable circumstances to ensure a rapid erosion of its substance, and consequent contamination of the water.

The rush of water necessarily produced by an intermittent flow must also detach portions of carbonate of lead from the sides of the pipe, even in those cases where the water has no very decided action on lead, and it is therefore far from improbable that in this manner the poison of lead is occasionally conveyed into our kitchens, and becomes mixed with our food.