Page images
PDF
EPUB

five million feet of pipe were sold during the year 1873 and sent to different parts of the country.

Inquiries addressed to the superintendents of the water works of Salem, Beverly and Cambridge, Massachusetts, and of Portsmouth, New Hampshire, where galvanized iron pipes have been used extensively for several years, have elicited replies, based upon the observation of the writers, the opinions of the water consumers and of reliable physicians and chemists whom they have consulted, to the effect that the use of these pipes is unattended with danger to health. The following extract, from the communication of Mr. D. H. Johnson, Jr., superintendent of the city water works in Salem, will serve to illustrate the general opinion expressed in the above and other communications received by the writer :

“It is only my province, as a practical man, to give you facts. We have, upon these works, 4,300 services inserted to the walls of buildings, containing 128,500 feet of galvanized iron pipes, or say 24 miles. There are as many more feet of pipes inside the walls of the houses, running (as generally the case) across the cellars to the back part of the houses, and then up to the draw-faucets in the sinks and to tanks in the top of the buildings. In round numbers, it is safe to say, 48 miles.

“Our medical men in this city have been consulted during the past five years upon the subject, and they have failed to trace, even in a single instance, any disease arising from, or to find any evidence of injurious effects from drinking-water drawn through such pipes."

In the extensive zinc and galvanized iron manufactories of Europe, practical experience and expert testimony

* have demonstrated conclusively that the workmen suffer no deleterious effects which could be ascribed to the zinc to which they are exposed in various ways. The same is true of the galvanizing works in this country. In reference to this point, communications have been received from the directors of large establishments in Philadelphia and Pittsburg, Pennsylvania, stating that "the workmen employed are as stout, strong, healthy and able-bodied men as can be found in any of our iron mills," and that none of them have ever been affected with any sickness which was attributed by themselves or physicians to the effects of the zinc to which they are constantly exposed. Some of them have been employed in these and in European manufactories for twenty years and more, without having experienced any ill effects, and still do a good day's work.

* Consult papers by Bouchet, Chevallier, Levy, Hirt and others, loc. cit.

Many entertain a suspicion that the use of these pipes and tanks may be dangerous, in consequence of the poisonous impurities which, it is said, the zinc coating may contain.

It is known that zinc ore contains many impurities. In the process of smelting, however, it is freed from these to a great extent, though not completely, and commercial zinc or spelter is never absolutely pure, but contains, generally, traces of sulphur, iron and arsenic (Brande and Taylor). Other authorities also mention, in addition to the above, lead, tin, cadmium and carbon. In the process of galvanizing iron, again, these impurities become separated from the zinc to a still greater extent, so that the zinc coating contains but the merest trace of them. The essentials of this process have been given before. The zinc is placed in large vats, generally holding about twenty tons, and subjected to a heat of about 7400 F. This heat necessarily expels nearly the whole, if not all, of the remaining sulphur and arsenic which were not separated from the original ore by the primary smelting process. At the same time the contained lead, iron, cadmium, etc., are melted with the zinc, but are rapidly deposited at the bottom of the vat, in consequence of their greater specific gravity. These precipitated matters form a waste, called the "dross," wbich amounts, in each vat, to six or seven thousand pounds weekly, and is shown by analysis to be composed as follows :

[ocr errors]
[ocr errors]

.

Zinc,
Iron, .
Tin,
Lead,
Balance of other metals,

94.88
3.55
1.00
.30
.27

.

100.00

The specific gravity of this dross is 7.06, while that of ingot zinc is 6.86. Now, as all iron is zinced from the top

a

of the vat, it does not come into contact with these impurities, which are at the bottom, and hence the zinc coating can contain but mere traces, if any, of them; at all events not enough to be the occasion of any deleterious effects upon the human system.

Most of the galvanizing in this country is done with the German spelter, which is preferred by manufacturers to the American article, notwithstanding its increased cost, " because it is thought to make the best finish, running brighter and thinner on the iron than the product of our native mines." Now this German zinc contains usually, according to numerous analyses, but a fraction of one per cent. of lead, the only ingredient which can possibly be the occasion of suspicion. As the greater portion of this minute quantity is precipitated to the bottom of the vats, the still more minute quantity which is present in the zinced product, evidently is unworthy of attention in the way of its endangering health.*

To recapitulate : it is proved theoretically, experimentally and practically that zinc is acted upon by ordinary drinkingwater; that water, allowed to stand in reservoirs or drawn through pipes of zinced or galvanized iron, usually contains an appreciable amount of zinc, more or less, according to various influences; that the zinc, contained in the water, is in the form of undissolved oxide and carbonate and of dissolved salts, the exact nature of the latter not being known; that probably under no circumstances is the oxide or the carbonate an active or gradual poison, much less in the amounts in which they can occur under the conditions mentioned ; that, at least with water fit for drinking purposes in other respects, the contained zinc salts in solution do not exert any deleterious effects upon the human system ; finally, that, even if all the zinc in solution were in the form of the chloride, which is known to be the most active poison of the zinc salts, the amount would still be insufficient to endanger health.

* Compare Rep. of State Board of Health of Mass. for 1871, p. 42, as to amounts of lead required to produce injurious effects.

HEALTH OF TOWNS.

« EelmineJätka »