As yet I have not been able to have any portion of the mass regularly slit and polished; but a surface of one of the larger compound concretions, on being ground upon its broader side and polished, afforded me an area of half an inch square. This face, on being subjected to the action of dilute nitric acid, gave me a series of markings altogether new. They are extremely fine and delicate in their dimensions, and require a strong light with the aid of a microscope, to be seen with distinctness. The first character that displays itself is somewhat that of a mesh or net-work, and arises from the polygonal boundaries of the granular concretions. The areas within these lines or edges (which are exceedingly thin) have a glittering luster when held at a fixed angle to the light, though this angle often varies for different concretions, as in the case of a polished surface of coarse grained calcite or fluor. The second character that arrests attention in the examination, is the finely striated surface of each concretion,-one set of lines being perfectly straight and equidistant, as in calcite and labradorite, while a second set, but less distinct, cross these at right angles. The final peculiarity of the markings consists in this, that these fine striæ are wholly made up of dots or beads, which are arranged in almost absolute contact, and are therefore to be regarded as consisting wholly of sections of rhabdite needles, while on the other hand, the mesh-like markings first noticed, are composed of plates of schreibersite.

From the foregoing it is apparent that the Auburn iron, when etched, is unlike any other hitherto described. But before a complete account can be given of its internal structure, an opportunity must be had of making further observations upon slices properly prepared from different portions of the mass.

The specific gravity, as obtained from four fragments, varied from 70-7·17, and gave 7.05 as the mean.

The iron is apparently free from chlorine. It dissolves in hydrochloric acid without extrication of sulphuretted hydrogen; and leaves behind a slight residue of thin brilliant, blackish scales and needles. The following result was obtained on about two grams weight of the iron:

Inasmuch as the iron analyzed was slightly enfilmed with oxyds, that, in the results obtained, had to be calculated back to the metallic state in common with the oxyds coming from the pure metals, a trifling part of the loss in the analysis should go to increase the iron and nickel above given.

The composition of the troilite, schreibersite and rhabdite in the mass is too well known to render necessary any attempt to analyze them in the present case. Neither cobalt, tin, nor copper was detected in this iron.

2. Meteoric Iron from Southeastern Missouri.

For my knowledge of this iron I am indebted to Prof. B. F. Shumard, of Saint Louis, who sent me a specimen of it several years ago, but through an accident it failed to reach me until lately. He wrote me under date of Nov. 4, 1868, as follows: "The specimen is from one in the collection of the St. Louis Academy of Sciences which I found among minerals that belonged to the old Western Academy of Sciences, of St. Louis. The label with it gives only 'S. E. Missouri' as the locality. Its meteoric character was not known until I examined it."

In reply to my request for further information, Prof. Shumard has favored me (Dec. 18) with the following additional particulars: "The specimen in the Academy's collection is irregularly lozenge-shaped, 3,3 inches long, 1 wide, and 1% thick. The extremities and upper face are rough and irregular, one lateral piece is smooth with a wavy surface, the other has been cut to supply specimens to Prof. Silliman, Haidinger and yourself. The under side is rough near one end, while the remainder of it has been smoothed by hammering. The specimen bears the appearance of having been heated. Its present weight is nine ounces; and if you will add to this what has been taken to furnish the specimens referred to above you will probably not be far from the truth, in calling the original weight twelve ounces. Nothing has been published concerning the specimen. I discovered it in the museum of the Academy during the year 1863."

In respect to the figures developed by etching, it belongs to my order of megagrammic irons; and most resembles those of Arva and Cocke county. It is rich in schreibersite, insomuch that when long acted upon by acid, this mineral projects in thick laminæ above the surface, resembling mica on certain weathered coarse grained granites. The bars and spaces which are intermediate, however, are not traversed by those delicate lines of the same substance, so generally occurring in other irons.

AM. JOUR. SCI.-SECOND SERIES, VOL. XLVII, No. 140.-MARCH, 1869.

Specific gravity 7·015-7-112. It appears to contain no chlorine. It gave:

Iron,
Nickel,

Schreibersite,

Chromium, cobalt, magnesium, phosphorus,

92.096

2.604

5.000

traces.

A fine residue of Fe Si and C. Neither copper nor tin was found.

3. Composition of Meteoric Iron from Losttown, Cherokee Co., Georgia.

My general description of this iron was contained in vol. xlvi, p. 257 of this Journal. Its analysis has afforded me

Iron,
Nickel,

Insoluble (schreibersite and rhabdite,) - - - - - -
Chromium, cobalt, tin (?), magnesium,-

Charleston, S. C. Dec. 29, 1868.

.95.759

3.660

0.580

..traces.

ART. XIX.-On Nitrification;* by S. W. JOHNSON.

Formation of nitrogen compounds in combustion.-Saussure first observed (Ann. de Chimie, lxxi, 282), that in the burning of a mixture of oxygen and hydrogen gases in the air, the resulting water contains ammonia. He had previously noticed that nitric acid and nitrous acid are formed in the same process.

Kolbe (Ann. Chem. u. Pharm., cxix, 176) found that when a jet of burning hydrogen was passed into the neck of an open bottle containing oxygen, reddish-yellow vapors of nitrous acid or nitric peroxyd, were copiously produced on atmospheric air becoming mingled with the burning gases.

Bence Jones (Phil. Trans., 1851, ii, 399), discovered nitric (nitrous ?) acid in the water resulting from the burning of alcohol, hydrogen, coal, wax, and purified coal-gas.

By the use of the iodid of potassium starch-test (Price's test), Boettger (Jour. für Prakt. Chem., lxxxv, 396,) and Schönbein (ibid., Ìxxxiv, 215,) have more recently confirmed the result of Jones, but because they could detect neither free acid nor free alkali by the ordinary test-papers, they concluded that nitrous acid and ammonia are simultaneously formedthat, in fact, nitrite of ammonia is generated in all cases of rapid combustion.†

*The substance of this paper was orally presented to the National Academy of Sciences, in August, 1868.

+ Nitrous acid does not appear when the combustible contains sulphur, since it is decomposed at high temperatures by sulphurous acid.

Meissner (Untersuchungen über den Sauerstoff, 1863, p. 283,) was unable to satisfy himself that either nitrous acid or ammonia is generated in combustion.

Finally, Zabelin (Ann. Chem. u. Ph., cxxx, 54), in a series of careful experiments, found that when alcohol, illuminating gas and hydrogen burn in the air, nitrous acid and ammonia are very frequently, but not always formed. When the combustion is so perfect that the resulting water is colorless and pure, only nitrous acid is formed; when, on the other hand, a trace of organic matters escapes oxydation, less or no nitrous acid, but in its place ammonia appears in the water, and this under circumstances that preclude its absorption from the atmosphere.

Zabelin gives no proof that the combustibles he employed were absolutely free from compounds of nitrogen, but otherwise, his experiments are not open to criticism.

Meissner's observations were indeed made under somewhat different conditions; but his negative results were not improbably arrived at simply because he employed a much less delicate test for nitrous acid than was used by Schönbein, Boettger, Jones and Zabelin.*

We must conclude then, that nitrous acid and ammonia are usually formed from atmospheric nitrogen during rapid combustion of hydrogen and compounds of hydrogen and carbon. The quantity of these bodies thus generated is, however, in general so extremely small as to require the most sensitive reagents for their detection.

Formation of nitrogen compounds at low temperatures.Schönbein was the first to observe that nitric acid may be formed at moderately elevated or even ordinary temperatures. As is well known he obtained several grams of nitrate of potash by adding carbonate of potash to the liquid resulting from the slow oxydation of phosphorus in the preparation of ozone.

More recently he believed to have discovered that nitrogen compounds are formed by the simple evaporation of water. He heated a vessel (which was indifferently of glass, porcelain, silver, &c.), so that water would evaporate rapidly from its surface. The purest water was then dropped into the warm dish in small quantities at a time, each portion being allowed

Meissner rejected Price's test in the belief that it cannot serve to distinguish nitrous acid from hydric peroxyd. He therefore made the liquid to be examined alkaline with a slight excess of potash, concentrated to small bulk and tested with dilute sulphuric acid and ferrous sulphate, (Unters. ü. d. Sauerstoff, p. 233). Schönbein had found that iodid of potassium is decomposed after a little time by concentrated solutions of hydric peroxyd, but is unaffected by this body when dilute, (Jour. für prakt. Chem. lxxxvi, p. 90.) Zabelin agrees with Schönbein that Price's test is decisive between hydric peroxyd and nitrous acid. (Ann. Chem. u. Ph., cxxx, p. 58.

to evaporate away before the next was added. Over the vapor thus generated was held the mouth of a cold bottle until a portion of the vapor was condensed in the latter.

The water thus collected gave the reactions for nitrous acid and ammonia, sometimes quite intensely, again faintly, and sometimes not at all.

By simply exposing a piece of filter paper for a sufficient time to the vapors arising from pure water heated to boiling and pouring a tew drops of acidified iodid of potassium-starchpaste upon it, the reaction of nitrous acid was obtained. When paper which had been impregnated with dilute solution of pure potash was hung in the vapors that arose from water heated in an open dish to 100° F. it shortly acquired so much nitrite of potash as to react with the above named test.

Lastly, nitrous acid and ammonia appeared when a sheet of filter paper, or a piece of linen cloth, which had been moistened with the purest water, was allowed to dry at ordinary temperatures, in the open air or in a closed vessel. (Jour. für Prakt. Chem., lxvi, 131). These experiments of Schönbein are open to criticism and do not furnish perfectly satisfactory evidence that nitrous acid and ammonia are generated under the circumstances mentioned. Bohlig has objected that these bodies might be gathered from the atmosphere where they certainly exist, though in extremely minute quantity.

Zabelin, in the paper before referred to (Ann. Ch. Ph., cxxx, p. 76), communicates some experimental results which, in the writer's opinion, serve to clear up the matter satisfactorily.

Zabelin ascertained in the first place that the atmospheric air contained too little ammonia to influence Nessler's test, which is of extreme delicacy and which he constantly employed in his investigations.

Zabelin operated in closed vessels. The apparatus he used consisted of two glass flasks, a larger and a smaller one, which were closed by corks and fitted with glass tubes, so that a stream of air entering the larger vessel should bubble through water covering its bottom and thence passing into the smaller flask should stream through Nessler's test. Nextly, he found that no ammonia and (by Price's test) but doubtful traces of nitrous acid could be detected in the purest water when distilled alone in this apparatus.

Zabelin likewise showed that cellulose (clippings of filter paper or shreds of linen) yielded no ammonia to Nessler's test when heated in a current of air at temperatures of 120° to 160° F.

Lastly, he found that when cellulose and pure water together