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was slightly warmed; the air thereby driven out was of course replaced with quicksilver, the upper surface of which, after the original temperature had been reëstablished, was marked. Now, if any decomposition of common salt occurred by the agency of lead, the chlorine would be freed from the sodium, the sodium would decompose the water, hydrogen would be set free, and the column of mercury depressed. Instead of any such result, the column of mercury regularly rose in every instance. An apparatus of this description, several months in action, is still preserved in my laboratory. It might still have been said, that, had the flask been deprived of air, the lead would have been acted on by the simple chloride. The experiment of lead and sea-water, in a flask deprived of air, has been made. The flask was sealed on the 25th of May last. The bar for a long time retained its perfect brightness, and is but very faintly dimmed at this late day, February 1, 1849.

“5. Action of Organic Matter. — It has been conceived that organic matter might exert a deleterious influence. Experiments already recorded (p. 15) show that the presence of organic matter increases the protecting power of water which is to be transmitted through lead. If the quantity exceed one ten-thousandth of the weight of the water, precipitates of oxide of lead, united to organic matter, take place. Orfila has remarked the precipitation of the coloring matter from Burgundy by neutralizing it with litharge.* Its influence in withdrawing the oxygen from solution has also been alluded to. In the important researches of Dr. Smith † upon the air and water of towns, it is mentioned that the presence of nitrates in the London water prevents the formation of organic matter, and that organic matter, in filtering through soils, becomes rapidly oxidated. Additional experiments bearing upon this point are recorded farther on.

Influence of Impurities in Water. — It is a prevailing conviction, that the more impure a water is, or, in general terms, the more salts it contains in solution, the less will be its action on lead. The influence of sulphate of magnesia (epsom salts) and chloride of sodium (common salt) in distilled water was the subject of experiment. The action, it will be seen, was more vigorous in distilled than in the impure waters.

Toricologie Générale, Vol. I. p. 616.

Proc. Brit. Ass. Athen., No. 1087.

“ Table XXII. - Experiments with Lead and Graduated Solutions of Sulphate of Magnesia (Epsom Salt).

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“ Table XXIII. — Experiments with Lead and Graduated Solutions of Chloride of Sodium.

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- Coats that form on Lead. - In seeking to ascertain the nature of the protecting coat which forms in all the waters hitherto experimented with, the influence of organic matter was first considered. 500cc. of each of several waters were evaporated to dryness over a water-bath. ignited, and redissolved in an equal measure of distilled water. There remained a small insoluble residue, which readily dissolved, with vescence, in hydrochloric or acetic acid, — indicating carb lime. Bars of lead were exposed to these prepared sol, bluish-white coat formed upon the lead in each.

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" TABLE XXIV. — Experiments with the several Waters deprived of their Organic Matter and Carbonate of Lime.*

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1 3.000 0.000 0.500 5.000 l 6.000 15.000 5.000 4.000 4 1.000 0.000 0.500 0.500 2.500 2.000 12.000 2.000 5' 1.500 | 0.010 | 0.010 | 0.020 8.000 1.000 15.000 0.500 $ 2.000 0.010 0.500 0.800 10.000 2.000 i 3.000 1.000 9 0.500 0.050 0.050 0.100 4.000 4.000 1.500 1.500 11 0.500 0.100 0.100 0.100° 0.800 0.100 0.100 0.100 18 0.500 0.800 0.800 | 0.800 20.000 30.000 0.800 0.500 37 | 1.500 | 1.000 2.000 / 1.250 12.000 3.000 0.700 | 1.500 42 1.250 | 1.000 1.000 2.000 2.000 20.000 8.000 0.100 44 15.000 1.500 1.000 0.800 0.200 0.100 0.100 0.100 47 '15.000 0.500 0.100 1.500 0.500 0.100 0.100 0.100 481 0.200 0.100 0.300 0.100 1.000 0.200 0.100 0.300 49 0.400 0.400 0.500 0.300 2.000 0.500 0.400 0.400 50 0.500 0.200 0.900 1.000 2.000 2.500 1.000 0.100 52 1.750 0.010 1.800 | 1.800 1.000 3.000 0.100 0.100

“ It will be seen, on comparing the results of their actions with those of the natural waters, that they are more protracted and vigorous, that they approach more nearly the action of distilled water, and that no protecting coat can be said to have formed. Three kinds of coating upon lead have fallen under my notice : a bluish-gray one, which, according to Winkelbleck, Mitscherlich, and others, is a simple suboxide ; a reddish one, which formed in Croton, Schuylkill, and Jamaica waters; and a white one. The coat of suboxide is insoluble in water. When the quantity of oxygen in solution in a given water is small, this coat will be first formed. It is the only one I have seen in Croton pipes less than two years in use. The addition to this coat of slimy organic matter, oxide of iron, and, to some extent, carbonate of lead, forms the reddish coat, the impermeable character of which, for all practical purposes, is illustrated in the appearance of Croton pipe five years in use, and already referred to. The white coat, it has been observed, consists chiefly of carbonates and sulphates. : - Solubility of Oxide of Lead. — I have already noticed the contrariety of opinion upon the solubility of the oxide of lead. I have repeated the experiments of Yorke, and confirmed his results, and am,

• Professor Silliman, Jr., has remarked of the alkaline reaction which the redissolved residues gave. The reaction of the above solutions was not observed. In their extreme dilution, an alkaline reaction could not bave been appreciable. .

moreover, satisfied that, had Thompson and Philips concentrated the filtrates which they supposed to contain no lead, they would have detected it without difficulty. A flask containing distilled water and lead shavings was corked and placed aside for a few days. A deposit of carbonate and hydrate of lead formed around and upon the lead shavings. The contents of the flask were carefully poured upon a double filter of Swedish paper, and the filtrate concentrated. It gave a distinct precipitate with hydrosulphuric acid.

Tea and Coffee Grounds unite with Lead in Solution. — It has been an occasion of surprise, that numerous families have for a long period employed well-water that corroded leaden pipe so rapidly as to require replacement in from six to eighteen months, and yet, so far as they or their physicians know, have suffered no illness attributable to the water. This fact suggested two considerations : – Ist. Are all lead compounds equally poisonous ? 2d. If so, is the quantity which finds its way into the organism sufficient to produce the maladies attributed to lead ? It may be assumed that water flowing directly through a leaden pipe of an inch bore and not more than thirty feet in length will ordinarily be identical in constitution with that in the source from which it is drawn. That only which has been some time at rest would be expected to contain lead. Accordingly, there is more care that the water first drawn be thrown away. The first morning draught is usually in the form of tea or coffee. The following experiments throw light upon this point. To boiling water containing lead in solution tea was added, in the quantity usually taken in the preparation of the beverage (a gramme to 50cc.), the temperature maintained three minutes just below the boiling point, and the decoction filtered off. The filtrate was evaporated to dryness, ignited, redissolved, and the precipitate with hydrosulphuric acid made and estimated as already described.

“I. 50cc. of lead solution, containing one thousandth of its weight of lead, with 1gr. of black tea, lost ninety-nine hundredths of its lead. Originally present,

0.05gr. of lead. After separation from the grounds, 0.0005" “ II. 55cc. of solution containing one tenth as much lead as the ' above, with the above quantity of tea, lost more than eleven twelfths of its lead.

Originally present in solution, 0.005gr. of lead.

After separation from the grounds, 0.0004 " “ The experiments with coffee yielded the following results :

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“ I. 50cc. of lead solution, containing one thousandth of its weight of lead, with 10cc. of coffee-grounds, were boiled three minutes, and the decoction poured off. The residue was drained through Swedish filtering-paper, the filtrate added to the liquor poured off, and evaporated to dryness, ignited, redissolved, treated with hydrosulphuric acid, and the precipitate estimated as before. It had lost more than fortynine fiftieths of the lead. Originally in solution,

0.05gr. of lead. After separation from the grounds, 0.0009 " “ II. 50cc. of solution, containing one tenth as much lead as that in the last experiment, were boiled with 5cc. of coffee-grounds, and treated as above. It had lost more than eleven twelfths of its lead. Originally in solution,

0.005gr. of lead. After separation from the grounds, 0.0005 " “ These results contribute to account for the circumstance mentioned above.

“ Other MATERIALS THAN LEAD FOR SERVICE-PIPES. — I have remarked that this investigation was instituted chiefly with a view to determine the trustworthiness of lead. Experiments have, however, to some extent, been made with other substances. The general conditions have been observed in experimenting with them that had been re. garded with lead, namely, equal volumes of water to equal surfaces of substance, that comparison might be instituted.

“ Table XXV. - Experiments with Copper Turnings. Water concentrated to one third of its volume.

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11 0.001 0.500 0.000 0.001 0.002 0.000 0.000 0.000 0.001 0.000 17 1.000 0.500 1.000 0.500 1.000 1.000 0.010 0.500 0.010 0.500 25 0.005 0.001 0.002 0.050 0.080 - 0.002 0.001 0.050 0.001 37 0.000 0.000 - 0.005 0.050 0.050 - 0.000 - 0.010

“ These experiments show only a feeble action of aerated water on copper.

“ TABLE XXVI. — Experiments with Tin. — The tin contained arse. nic as an impurity. Chemically pure tin yielded precisely the same results when exposed to the same waters. Bars of size already men. tioned. 10cc. of water concentrated to from 3 to 5cc. Precipitates

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