JOURNAL

OF THE

FRANKLIN INSTITUTE

OF THE

State of Pennsylvania,

DEVOTED TO THE

MECHANIC ARTS, MANUFACTURES, GENERAL SCIENCE,

AND THE RECORDING OF

AMERICAN AND OTHER PATENTED INVENTIONS.

JULY, 1835.

Engraving on Wood.
(SEE VIGNETTE.)

We present the readers of the Journal with a wood-cut, engraved by our fellow member, Mr. Reuben S. Gilbert, of this city, representing a scene taken from Burns' celebrated poem of "Tam O'Shanter," and copied from an engraving of Thomas Landseer's.

In a former number, (vol. x., p. 145,) we presented to our subscribers a beautiful specimen of medal ruling, which has excited much admiration, both at home and abroad; and we hope hereafter to offer further illustrations of the condition of the arts in our country.

Few persons, except artists, can fully appreciate the merits of this engraving as a specimen of the art, but it will, we apprehend, be generally conceded, that the entire performance will bear a strict comparison with the best European efforts in the same style.

The story which this cut is intended to illustrate, is too well known to our readers to need a description of the action of the piece, with the merit of the composition of which we have, besides, at present, no concern. Our object is to call attention to the engraving as a specimen of the art, and to the full enjoyment of it, in this point of view, the subject matter is unessential. COм. PUB.

VOL. XVI.-No. 1.-JUNE, 1835.

1

On the comparative Corrosion of Iron, Copper, Zinc, &c., by a saturated solution of common salt. By A. D. BACHE, Prof. of Nat Philos, and Chem., Univ. Penn.

TO THE COMMITTEE ON PUBLICATIONS.

GENTLEMEN,-An inquiry was addressed to me some months since, by Mr. Joseph S. Walter, Jr., in relation to the material which would be most proper to be used for pipes to convey a strong solution of common salt to a pump intended to raise it, and for the material of the pump itself. From this solution it was intended to recrystallize the salt. The circumstances being of a somewhat complex character, I determined not to be satisfied with the indications of general theory, but to try the experiment, under the circumstances of the case, as nearly as might be possible. The materials in relation to which inquiry was particularly directed, were iron, copper, brass, lead, and zinc. Of these, the rapid oxidation of iron, when exposed to a solution of common salt, is well known; the corrosion of copper by seawater is also well known; the influence of the earthy muriates contained in the ocean prevents this case, otherwise very closely resembling that in question, from corresponding precisely to it, the common salt referred to containing these muriates only as impurities. Zinc does not decompose water readily, and oxidates very slowly, even when exposed to the combined action of air and moisture; it also ranks below sodium in the list of electro-positive metals; its chloride, however, is soluble. Lead is readily acted upon by the combined agencies of air and water, first oxidating, and then passing to the state of a carbonate; its place in the list of positive electrics is below zinc, and, of course, below sodium, which latter we should expect, therefore, to have the greater affinity for chlorine; the protoxide of lead, however, and several of its salts, interchange elements with chloride of sodium. The chloride of lead is insoluble, and hence the presence of soluble muriates acts as a protection against the corrosion of lead by water.

As the experimental results directly obtained may possibly prove of value to others than the estimable individual for whom they were to be applied, I have thought it right to put them on record.

The materials used were iron, copper, brass, lead, and zinc, the metals being as presented in commerce, and, therefore, probably not quite pure. They were prepared in rectangular plates, about two and a half inches in length, and three-fourths of an inch in width, and varied in thickness from .03 to .07 of an inch. These were placed in glasses containing saturated solutions of common salt, rather less than one-fourth of an inch in depth from the top of each plate being left exposed to the air. The vessels were left uncovered, and the evaporation of the water of the solutions was supplied from time to time during the exposure. The temperature in the room in which the vessels were placed, was not very different from 50° Fahr. during any part of the time.

After an exposure of about three weeks, the plates were removed from the solutions, and carefully washed and dried. Having been weighed before placing them in the solutions, they were now again weighed, and the loss of weight ascertained.

The iron plate was found covered with oxide of iron, strongly ad

hering to it in part, and in part deposited at the bottom of the glass containing the solution. There was upon the upper plate, and in the glass, a deposit of proto-chloride (white) of copper, coloured by carbonate of copper, and a similar deposit upon the brass plate. The lead and zinc had been, to all appearance, very slightly acted upon; there was upon the latter a white deposit, probably of oxide of zinc. The following table shows the amount of surface actually exposed to the solutions, the weight of the entire plates, and the loss of weight by the exposure. I have not reduced the weights used to grains, because the object is merely to obtain comparative results.

From the foregoing data I have calculated, below, the loss of weight, in grains, which a surface of forty square inches, or a plate of twenty inches on each surface, and very thin, of the materials would have suffered, and the relative loss by each material, referring to that which lost least, namely, the zinc, as the standard of comparison.

The corrosion of the iron, with the same extent of surface as zinc, and exposed to a solution of common salt for the same length of time, is thus shown to be upwards of one hundred times that of the zinc. The zinc appears to protect the copper in the brass, probably by rendering it electro-negative, and thus diminishing the affinity of the chlorine, which would otherwise destroy the copper.

Since the experiments indicate zinc and lead as the materials to be selected from those named, on account of the slight corrosion which they suffer, lead would obviously have been the material selected for the pipes to conduct the solution of salt to the pump, and zinc for the material of the pump, the selection depending upon well known properties of these metals.

The coatings formed upon both the lead and zinc, would protect the underlaying surface from action, unless removed by mechanical force.

First Report of the Joint Committee of the American Philosophical Society, and Franklin Institute, on Meteorology.

The Joint Committee of the American Philosophical Society, and the Franklin Institute of the State of Pennsylvania, return thanks for valuable meteorological journals, received from the following gentlemen.

Mr. R. H. Gardiner, Gardiner, Maine.

Mr. Jacob Mull, U. S. Navy, Portsmouth, New Hampshire.
Mr. James Porter Hart, Farmington, Mass.
Professor Caswell, Providence, R. I.
Mr. A. W. Smith, Middletown, Conn.
Mr. Edward Gibbons, Lockport, N. Y.
Mr. C. Gill, Flushing, Long Island.
Dr. R. H. Rose, Silver Lake, Pa.

Dr. Henry Gibbons, Wilmington, Del.

Dr. G. S. Sproston, U. S. Navy, Baltimore, Md.

Dr. J. M. Foltz, U. S. Navy, Washington city, D. C.
Prof. James Hamilton, Nashville, Tenn.

Dr. John Locke, Cincinnati, Ohio.

Mr. J. Panglos, Urbana, Ohio.

Only four months have elapsed since the reception of the earliest of these journals, and already some valuable facts have been deduced from a comparison of the simultaneous observations which they contain.

A detailed report of all general conclusions, with the data on which they are founded, will be given hereafter; but as this will require a considerable length of time, and a much more extensive collation of journals than the committee have yet in their possession, they will mention, with a view to increase the zeal of their correspondents, one or two facts, which, from further observations, will probably lead to important general laws.

In all the great fluctuations of the barometer which occurred in January and February, at Nashville, Tenn. they were one day sooner than at Philadelphia; and on the 22d of March, the barometer was lowest at Philadelphia at 3 o'clock, P. M.; whereas, at Providence, R. I., it continued to fall till 9 o'clock, P. M., as very particularly noted by Professor Caswell. The exact moment of greatest depression at Portsmouth is not given by Mr. Mull, but it was lower there at 7 o'clock, P. M. on the 23d, than on the 22d at sunset; at which time it had already risen more than half an inch at Philadelphia.

Do these barometric fluctuations of great magnitude travel north-eastwardly?

Again, on the 22d of March, at the moment when the barometer was lowest at Philadelphia, the wind at York, Pa., at Flushing, N. Y., at Middletown, Conn., at Providence, R. I., and at Portsmouth, N. H., was blowing towards Philadelphia violently, especially at York and Portsmouth, while at Philadelphia it was a perfect calm. There was also, on that day, a very violent rain at York, and in