"Well in Boston. 200cc., first drawn in the morning, gave, when concentrated to 5cc., 0.00003gr. = 0.00068gr. in a gallon. Dr. Charles T. Jackson has detected lead in a well-water in Waltham. "Well in Dedham. 100cc. of water standing over night in the pipe serving from the reservoir supplied by a forcing-pump, concentrated to 5cc., gave a trace of lead. "Water supplied from the spring in Dedham, which is known to have corroded leaden pipes, and poisoned at least one individual. — 100cc., at rest twelve hours in leaden pipe several years in use, gave 0.00003gr. = 0.0013gr. in a gallon. Several years since, my friend, Dr. Webster, examined some of this water from the pipes of the gentleman who was made ill, and detected lead, without concentration, by treatment with sulphide of ammonium.* This branch pipe was 150 feet in length. The main pipe, two inches in diameter, is about three quarters of a mile long. This pipe must be capable of holding a gallon in a little more than seven and one third feet, or 540 gallons in its whole length. Thus, the entire morning draught of spring water of each * Such was the quantity of lead in solution, that a white film (of carbonate and hydrate of lead) rose to the surface of this water, after being drawn a short time. family had ordinarily been at rest twelve hours in the main and lateral pipes. In some instances it had doubtless been longer at rest; and yet, so far as I have been informed, but one well-established case of lead disease is known to have occurred from the use of this water. “TABLE XVII. — Determinations of Lead in the Croton Water of New York. Drawn, after thirty-six hours' exposure, from leaden pipes, at seven different localities, in the neighbourhood of John Street. Bottles. 500cc. reduced to 10cc. gave, of Sulphide of Lead, 00 1. 2. "1000cc. derived from bottles 1, 2, and 3, concentrated to 10cc., gave, with hydrosulphuric acid, a precipitate which, ignited with saltpetre and redissolved, gave, with bichromate of potassa and hydrosulphuric acid, distinct precipitates of lead. The whole quantity equalled about 0.0001gr., or for a gallon 0.00045gr. "Determination of Lead in the Schuylkill Water of Philadelphia. - According to Professor Booth, 100 apothecaries' ounces, after exposure 36 hours in leaden pipe, a year and a half in use, concentrated to the bulk of half an ounce, gave not the slightest discoloration after transmitting hydrosulphuric acid through it for an hour. "Troy Reservoir Water.. · 2000cc., 24 hours at rest in leaden pipes several years in use, gave, when concentrated to one hundredth of its volume, no trace of lead. "TABLE XVIII. Determinations of Lead in Jamaica Water served through leaden Pipes in the City of Boston. "April 13th. Worcester Railroad Depot, 1000cc., exposed to the lead 36 hours, reduced to 20cc. gave, of sulphide of lead, 00gr. "June 19th. Worcester Railroad Depot, 500cc., exposed to the lead 36 hours, reduced to 5cc., gave, of sulphide of lead, 0.00002gr.* = 0.00018gr. in a gallon. "The magnitude of this quantity, and the influence its known presence in a water should have, may be over-estimated. 500 cubic centimetres contain 0.00002gr. "Wiesbaden water contains of arsenious acid, in 1000cc., 0.00045gr.,† a quantity more than ten times as great as the lead in Jamaica water, and yet this water is renowned for its medicinal virtues. It may be said, that the arsenic is in combination with oxide of iron. Chevallier and Gobley have come to the conclusion, that its occurrence in springs is not dependent upon the presence of iron. It is found in water whose character is determined by the presence of carbonic acid or sulphates. This body occurs in solution in waters from nine mineral springs in France. Its occurrence in Germany has been recognized, among others, by Will. Tripier found it in Algiers. "The appearance of leaden pipes taken up after several years' use, in New York, is what might have been expected. I have examined twelve pieces from as many different localities. Most of the specimens that had been in use for only one and two years were covered with a bluish-gray coat, and some of them could scarcely be distinguished from ordinary pipe for sale in the shops. A specimen in use five years is coated with a transparent, exceedingly thin, reddish-brown film, apparently composed of organic matter, oxide of lead, and oxide of iron. The crystalline laminæ upon the inner surface, characteristic of new pipe, are to be seen with the utmost distinctness, and present, with the exception of the coating, no appearance distinguishing it from new pipe. "Jamaica pipe, in use from fifteen to twenty years, is coated with a thick, reddish coat, which, when dry, may be readily disengaged, and in one specimen examined shows traces of slight corrosion beneath. The corrosion from without was such as to have nearly eaten through in some places. The lead of this pipe contained great proportions of antimony where corrosion occurred, but no sulphide of lead, which, I am informed, occurs in much lead pipe. * Precipitate ignited, redissolved, and re-precipitated. "Pipe employed to conduct Dedham spring water is internally corroded, and presents at intervals deep depressions, the result of more extreme local action. Pipe of one well in Cambridge is appreciably corroded. Pipe of wells in Boston is frequently consumed in periods of from six to eighteen months. "The above results and observations show, that, "1st. Many well-waters, in a space of time comparatively short, act on lead. This has been fully established by the researches of Dr. Dana in this country, and by observations in England. "2d. That, except after longer exposure than will ordinarily occur in actual use, the amount of lead coming into solution in Croton, Schuylkill, or Jamaica waters is too small to occasion any solicitude. "Hence it may be inferred from the above, and from the great similarity of Cochituate to Jamaica, Croton, and Schuylkill waters, in its relations to lead, that the quantity of lead that will be dissolved in Cochituate water in actual service will, for all practical purposes, be of no moment. "The recognition and quantitative determination of very minute quantities are not always without difficulty; where many and rapid determinations are required, the processes of gathering upon a filter, washing, drying, igniting, and weighing consume far too much time, and are sometimes less accurate than other and more indirect methods. That which I have employed is based upon the mode of analyzing silver coin proposed by Gay-Lussac, † and adopted quite universally at mints. The same general method has been extended by Gay-Lussac to ascertain the strength of alkalies and bleaching-powder. It is employed with protosulphate of iron and subchloride of mercury for the latter purpose. It is the method of graduated solutions. A gramme of lead in the form of the acetate (common sugar of lead), which contains three atoms of water, is dissolved in 100 grammes or parts of distilled water. This constitutes solution No. 1. Ten parts of this solution are diluted with ninety parts of water to make solution No. 2. Ten parts of solution No. 2, diluted with ninety parts of water, make solution No. 3. In the same manner solutions No. 4, No. 5, and No. 6 are prepared. "Ten parts of each solution are placed in corresponding test-tubes (about six inches long, five eighths of an end), and hydrosulphuric acid transmitted Appendix to Tanquerel, by Dana. inch wide, and closed at one through them till the liquid, Annales de Chemie et de Physique. first blackened by the formation of sulphide of lead, becomes clear. Test-tube No. 1 contains one tenth of a gramme of lead in the form of sulphide, a black powder at the bottom. Test-tube No. 2 contains one hundredth of a gramme. No. 3, one thousandth. No. 4, one tenthousandth. No. 5, one hundred-thousandth. No. 6 yielded no precipitate without concentration. Each succeeding precipitate in the series, setting aside a slight allowance to be made on account of solubility, was one tenth as voluminous as the one above. 66 Having prepared this scale of quantities, it is required to determine the amount of lead in a given diluted solution. An experiment is made to ascertain if the quantity be large enough to give a direct precipitate with sulphide of ammonium. This being decided in the negative, fifty cubic centimetres or grammes of water (corresponding with fifty parts of the scale of solutions) are carefully evaporated to dryness and ignited in a small porcellain capsule (to expel any organic matter that may have been present), moistened with nitric acid, and then warmed, with the addition of acetic acid and water, till the volume becomes ten cubic centimetres. A drop of acetate of potassa is then added, and then hydrosulphuric acid gas transmitted through the solution. A precipitate results, or it does not. If it does, to know its value or the amount of lead it contains, the scale is resorted to. Though it might rarely be possible to identify it with either one of two precipitates in the scale, there could be no difficulty in deciding between which two it should fall, or nearest to which one of two it should be placed. If fifty cubic centimetres thus treated yielded no precipitate, one hundred cubic centimetres were evaporated to dryness, and the residue similarly treated. If this failed, five hundred cubic centimetres were taken, and in some instances more, and the same course pursued. "It was natural to suppose that the presence of foreign bodies, such as occur in natural waters, might embarrass the precipitation. This led to the preparation of a series of graduated solutions of lead, with all the common salts occurring in waters, from the reagents in my laboratory. They were similarly treated with acetate of potassa, free acetic acid, and a stream of hydrosulphuric acid, and though it was possible to see differences in the amounts of the precipitates, they fell very greatly within the differences between the successive members of the graduated series. "The precipitates in the experiments with bars of lead, the results of which are given in the preceding tables, were estimated from this scale. |