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them with carbonate of soda, which will certainly be productive of some error; and although it is to be regretted that our methods of arriving at phosphoric acid in analysis may be diminished by this fact, still it will only stimulate us to find out some other to solve this, one of the most difficult and annoying problems in analytical chemistry.
REMOVAL OF SAL AMMONIAC IN MINERAL
About twenty years ago, in a publication made upon the analysis of the natural silicates, I gave the details of some interesting experiments made upon the removal of sal ammoniac, which so commonly accumulates in these analyses.
The method of accomplishing the removal of this salt, being embodied in a lengthy paper embracing many other and more important points, has been to a great extent overlooked by analytical chemists. I have been frequently asked for details in connection with the removal of this salt, and some recent investigations have given me renewed appreciation of the invaluable nature of the process, where very large quantities of sal ammoniac had accumulated and remained associated with a very minute quantity of material that formed the subject of research.
- It may be of interest to bring this process more clearly to the attention of chemists. The manner of proceeding is as follows: The solution containing the sal ammoniac is concentrated in a capsule, best over a water-bath or in a glass flask; pure nitric acid is added, about three grammes of it to every gramme of sal ammoniac supposed to exist in the liquid; a little habit will suffice to guide one in adding the nitric acid, as even a large excess has no effect on the accuracy of the analysis. The flask or capsule is now warmed very gently, and before it reaches the boiling-point of water a gaseous decomposition will take place with great rapidity. This is caused by the decomposition of the sal ammoniac. It is no advantage to push the decomposition with too great rapidity; a moderately warm place on the sand-bath is well adapted for this purpose. I, however, prefer a porcelain capsule of about three and a half to four inches diameter (in the ordinary operations in mineral analysis), inverting a clean funnel of smaller diameter over it,
REMOVAL OF SAL AMMONIAC IN MINERAL ANALYSIS. 271
and evaporating to dryness over the water-bath; at the end of the operation the heat can be increased to four or five hundred degrees.
By this operation, which requires no superintendence, one hundred grammes of sal ammoniac may be separated as easily and safely as one gramme from five milligrammes of alkalies, and no loss of the latter be experienced.
The following are some experiments made with given quantities of sal ammoniac and nitric acid, heated thus in a capsule over a water-bath:
5 grammes of sal ammoniac...
Sal Ammoniac 3.190 grammes.
The decomposition commences before the temperature reaches 140° Fah. The results of the decomposition were fully explained in a note to an article of mine published in the Amer. Jour. of Science and Arts, March, 1853. It results principally in the formation of protoxide of nitrogen and chlorine, the former constituting over seven eighths of the gas formed.
MEMOIR ON METEORITES.
A DESCRIPTION OF FIVE NEW METEORIC IRONS.
1. METEORIC IRON FROM TAZEWELL COUNTY, E. TENN.
This meteorite was placed in my possession through the kindness of Prof. J. B. Mitchell, of Knoxville, in the month of August, 1853. It was found by a son of Mr. Rogers, living in that neighborhood, while engaged in plowing a hillside; his attention was drawn to it by its sonorous character. As it very often happens among the less informed, it was supposed to be silver, or to contain a large portion of that metal. With some difficulty the mass was procured by Prof. Mitchell and passed over to me. Nothing could be ascertained as to the time of its fall. It is stated among the people living near where the meteorite was found that a light has been often seen to emanate from and rest upon the hill-a belief that may have had its foundation in the observed fall of this body.
The weight of this meteorite was fifty-five pounds. It is of a flattened shape, with numerous conchoidal indentations, and three annular openings passing through the thickness of the mass near the outer edge. Two or three places on the surface are flattened, as if other portions were attached at one time, but had been rusted off by a process of oxidation that has made several fissures in the mass so as to allow portions to be detached by the hammer, although when the metal is sound the smallest fragment could not be thus detached, it being both hard and tough. Its dimensions are such that it will just lie in a box thirteen inches long, eleven inches broad, and five and a half inches deep. The accompanying figure gives a correct idea of the appearance of this meteorite
The exterior is covered with oxide of iron; in some places so thin as hardly to conceal the iron, in other places a quarter of an inch deep. Its hardness is so great that it is almost impossible to detach portions by means of a saw. Its color is
white, owing to the large amount of nickel present; and a polished surface, when acted on by hot nitric acid, displays in a most beautifully regular manner the Widmannstättian figures. The specific gravity taken on three fragments selected for their compactness and purity is from 7.88 to 7.91.
The following minerals have been found to constitute this meteorite: 1. Nickeliferous iron, forming nearly the entire mass. 2. Protosulphuret of iron, found in no inconsiderable quantity on several parts of the exterior of the mass. 3. Schreibersite, found more or less mixed with the pyrites and in the crevices of the iron, in pieces from the thickness of the blade of a penknife to that of the minutest particles. 4. Olivine; two or three very small pieces of this mineral have been found in the interior of the iron. 5. Protochloride of iron; this mineral has been found in this meteorite in the solid state, which I believe is the first observation of this fact; it was found in a crevice that had been opened by a sledge-hammer, and in the same crevice schreibersite was found. Chloride of iron is also found deliquescing on the surface; some portions of the surface are