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They were, however, not ignited and redissolved, as in the examination of waters exposed in lead pipe, and the numbers were intended, as al. ready remarked, to express only relative values.

Influence of Nitrates. — Although medical testimony and public sentiment were conclusive upon the subject of the health of our larger cities, so far as it might be influenced by the lead contained in the reservoir-waters used for culinary and general purposes, it was equally certain that individuals had been poisoned from drinking the waters of wells, and in one case, at least, from drinking water from a spring. It was obvious, therefore, that between these two classes, river, lake, pond, and open reservoir waters on the one hand, and well and some spring waters on the other, there must be differences in their relations to lead. Experiments were made with well-water, and at the same time with the river and lake waters in my possession. The following result shows with what success.

Table XIX.

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“ The bars rested on the bottoms of the tubes, and the waters had been some time standing in sunlight. These experiments threw little light upon the subject. The differences in favor of the Cochituate and Fairmount, as compared with a well-water known to act vigorously on lead pipe, were too inconsiderable to be worthy of notice. These waters contained in 500cc. or Solid Residue.

Of Organic Matter. Or Inorganic Matter. Well water, 0.1380gr.

0.0540gr.

0.0840gr. Cochituate, 0.0267

0.0122

0.0145 Fairmount, 0.3007

0.1032

0.1975 “On comparing these, it will be seen that the water which contained the most solid residue acted least on lead, and that the action of that which contained least solid residue was next in order. The comparison of the analyses of waters made by different individuals led to no satisfactory results. Ingredients that might have been presumed to VOL. II.

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be in all had in some cases not been recognized. The only large suite of analyses made by a single individual first fell under my eye in the early part of June of 1848. In the following table are compared the average total amounts of inorganic matters, and also the relative amounts of the more prominent salts, in three wells, six springs, and six rivers, as determined by Deville. *

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“ The compounds of sulphuric and carbonic acids with oxide of lead are eminently insoluble. The chlorides are less insoluble, and the nitrates are highly soluble. The contrast between the quantities of ni. trates in well and river waters suggested the experiment with lead and graduated solutions of saltpetre. The results follow.

Table XX.

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* Ann. de Chem. et de Phys., 3. Série, Tom. XXIII., pp. 33 – 47.

Sulphate of lead is soluble in not less than 15000 parts of water. GMELIN. Carbonate of lead requires 50551 parts of water. FRESENIUS, Ann. der Chem. und Phar., LIX., S. 117 - 128. — Chloride of lead requires 135 parts of pure water, 534 of water containing chloride of calcium, and 1636 of water containing hydrochloric acid. Bischof. — Nitrate of lead dissolves in 1.989 parts of water at 63° Fahr. KARSTEN. — A solution of saltpetre containing 39 parts to 100 of water will still dissolve 110 parts of nitrate of lead. - GMELIN.

O'Henry found nitrates in mineral spring-water in 1839. Journ. de Pharm., Dec., 1838, pp. 634 – 637. – Liebig found nitrates in twelve wells in Giessen, and none in the wells of the surrounding country, by experiments made in 1827. “ This fact has been noticed by Berzelius in Europe. I," says Dr. Dana,“ have

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“ The mode of action of the saltpetre has been the subject of experiment. I had previously exposed bright bars of lead to natural waters containing traces of nitrates, which were deprived of air and sealed in glass flasks. Months had produced no action upon the lead, and had conducted to the opinion, that lead was not acted upon by nitrates in natural waters. As the reaction of the Cochituate or Fairmount water was perfectly neutral, the decomposition of the saltpetre by free acid, which should expose the lead to uncombined nitric acid, was not possible. Fresenius had observed that the carbonate of lead was less soluble in water containing nitrate of ammonia and ammonia than in pure water. I was aware that alkaline chlorides promoted the solution of certain lead compounds, and it occurred to me that they might be more soluble in waters from the presence of nitrate of potassa, soda, or lime.

“ In changing the waters, from day to day, exposure to the air would furnish the oxygen and carbonic acid more directly than the absorption from the surface, for the formation of the hydrated oxide and carbonate, and these might to a slight extent, it seemed possible, experience

confirmed it in the water of a great number of wells in Lowell.” Appendix to Tanquerel, p. 367. – Guyton Morveau, most of whose labors belong to the last century, mentions saltpetre as one of the salts denominated by him protecting in its influence on leaden pipes, when seeking to find the value as protectors of the different salts occurring in natural waters. CHRISTISON. – Dr. Dana has ascribed a prominent place to nitrates and chlorides in the action of well-waters upon lead. Appendix to Tanquere. — Experiments with graduated solutions of common salt were made. See p. 74.

decomposition with the saltpetre. The decision of this point rested up. on the following experiments.

“1. A solution of saltpetre, the usual laboratory reagent, was poured upon a quantity of common white lead, and, after repeated agitation and alternate rest, filtered off and tested with hydrosulphuric acid for lead. There followed an instantaneous, distinct, though not large, precipitate of sulphide of lead. There was an objection to the experiment. White lead prepared from the acetate might not be altogether free from acetate of lead. This, if present, might be brought into solution by the nitrate of potassa.

“ 2. To settle this point, a portion was carefully ignited upon platinum. Had there been appreciable acetic acid, the mass would have more or less blackened, or would have revealed to the sense of smell -some evidence of its presence. It gave no indication whatever.

“ 3. A quantity of the white lead was then treated with sulphuric acid and alcohol in a test-tube, in the usual manner for detecting acetic acid by the formation of acetic ether. This failed to give a trace of acetic acid. The quantity of white lead was small.

“4. Four ounces of white lead were then boiled three hours with a large measure of diluted soda, filtered, concentrated, and treated with sulphuric acid and alcohol as before. It yielded no distinct trace of acetic acid.

“5. To meet the question fully, and give to the experiment the advantage of the nascent state which in actual practice must occur, and to give to the view an entirely unobjectionable foundation, I added to a solution of nitrate of lead, first, potassa, which threw down a hydrate of lead, and then carbonate of potassa, which threw down a carbonate of lead, until the solution yielded an alkaline reaction. There were then hydrate and carbonate of lead in the precipitate, and nitrate of potassa, carbonate of potassa, and if any lead, a nitrate of lead in solution. The liquor was filtered, and, upon adding hydrosulphuric acid to the filtrate, I obtained a precipitate of the black sulphide, more voluminous than in the first experiment with white lead and a solution of saltpetre.

“6. Soda and carbonate of soda gave the same reaction.

“7. Nitrate of lime in solution gave the same reaction as nitrate of potassa.

“My attention has been drawn by a friend to the following sentence in Berzelius : — When nitrate of lime is boiled with carbonate

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of lead, the oxide of lead is dissolved, while the carbonate of lime is deposited.'* If with the aid of heat such decomposition results, it might be conceived that, favored by the nascent condition, quantity, and time, there might be to some small extent a corresponding decomposition. The first was the principal experiment bearing on this point made at the date of my last letter to the Water-Commissioners, and upon this experiment, and the known solubility of the nitrate, I ascribed the increased action of water consequent upon the addition of nitrates to a slight double decomposition. It had been ascribed by Dr. Dana † to the conversion of the protoxide of iron, in solution as protosulphate, into the peroxide, by which he conceived there would be free sulphuric acid, and therefore free nitric acid, in water containing protosulphate of iron and nitrates. $ This explanation would not apply to the action of Deutral waters, or of those containing no protosalts of iron, though ni. trates were present. The whole subject has undergone a more thorough examination. The conclusion that nitrates are not reduced by lead I have found to be erroneous ; for experiment has shown that upon boiling a strong solution of nitrate of potash to expel the air, and introducing a bar of bright lead, it became immediately coated with suboxide of lead, and this without the evolution of gas. There had been a partial reduction of the nitric acid. Upon testing the solution with hydrosulphuric acid, it gave, after long digestion, but a faint discoloration. Upon pouring off the liquor and adding to it oxide of lead, and continuing the digestion, a large quantity of lead was dissolved, which in 66cc. gave of sulphide of lead 0.0106gr.= 0.7296gr. in a gallon. The solution reacted strongly alkaline. As the only known inorganic salts of nitrous acid are its compounds with lead, it was probable that, upon the reduction of the nitric acid to nitrous acid, it had abandoned

• " Lorsqu'on fait boullir du nitrate calcique avec du carbonate plombique il se dissout de l'oxyde plombique tandis que le carbonate calcique reste.” — Traité de Chemie, 1847, Tom. IV., p. 91.

1 Report of the Joint Special Committee of City of Lowell, Aug., 1842, pp. 8-11.

| The change that takes place when a solution of copperas is exposed to the air may be thus represented : – 4 (Fe 0, 803) + 20 =Fe2 03, 3 S 03 + Fe, 03, S 03. The latter compound is insoluble in water. GMELIN. — The constitution of the precipitate, according to MITSCHERLICH and SCHEERER, is 2 Fe, 03, S 03 + 3H 0. WITTSTEIN (Buch. Rep., 3 R., Bd. I., S. 182 - 189) gives it as 2 Fe, 03 +3 803 + &HO. An acid salt remains in solution, which is probably what Dr. Dana would have understood from the statement that the above decomposition produces free sulphuric acid.

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