On account of the large consumption of oxygen in burning rapidly a considerable weight of oil, at least three times the quantity theoretically required for oxidation, and finding that the combustion proceeds with equal facility in air, nearly all our determinations have been made in a current of air supplied under pressure, with the same means for exhaustion that Burton found advantageous. The operation requires close attention and 0.5 to 1 gram of oil may easily be burned in forty-five minutes to one hour, depending upon the nature of the substance, the heavier oils especially if containing much sulphur being the most difficult to burn. The higher sulphides will not support a continuous flame, and dependence must be placed upon a very hot tube; with the more volatile oils it is sometimes difficult to maintain a continuous flame even in oxygen, the combustion proceeding in long intermittent non-luminous flashes. If the flame becomes luminous the rapidity of volatilization must be instantly checked, and the flow of air increased. The appearance of white fumes in the forward part of the combustion tube or the absorption tube, indicating improper adjustment as to the temperature, flow of gas, or rate of volatilization, is invariably attended with low results. The completeness of the absorption in the U tube was tested by placing a second tube beyond it containing a similar solution, but no trace of acid was found in the second tube when the excess of alkaline hydrate in the first at the end of the analysis was not less than 15-20 c. c. With a smaller excess in rapid combustions there is danger of loss. The oil for analysis is weighed in a bulb or tube of hard glass, and it is sometimes convenient to transfer most of it to a platinum or a porcelain boat, which may easily be accomplished without loss within the combustion tube provided there is a gentle current of air inward and the combustion tube in front has previously been heated to the required temperature.

In the examination of Ohio and Canadian sulphur petroleums for identification of the paraffine, aromatic, and unsaturated hydrocarbons, sulphur compounds, and other constituents, with which I am at present engaged, numerous determinations of sulphur have been necessary, and the extreme convenience of combustion in air has greatly facilitated the separation of the various products. As an evidence of the reliability of this method, the following results are selected with parallel determinations by the Carius method :

These results were obtained by six persons working independently of one another.

The oxidation of nitrogen to any considerable extent by the use of air in the combustion of sulphur compounds is evidently excluded by the close agreement of the results it yields with corresponding determinations by the Carius method. In accordance with the suggestion of a friend, from the fact that nitrous and nitric acids are formed to a greater or less extent depending upon conditions in the ordinary forms of combustion, it seemed of interest to ascertain whether these acids were present at all in the alkaline absorbent. In testing for the formation of nitrous acid, the exceedingly delicate color reaction was applied which is produced in an acid solution of a nitrite by the addition of sulphanilic acid and naphthylamine chloride. An

examination of our reagents showed that the purest commercial sodic or potassic hydrate gives an intense color, and even hydrates prepared from the metals are not free from color. Pure sulphuric acid gave no reaction, and pure sodic carbonate only a faint color. We finally obtained a solution that gave not a trace of color by dissolving metallic sodium and boiling the solution for some time with metallic aluminum. With this solution as the absorbent in a combustion of a sulphur oil, after the analysis the solution was as free from color as before when it had stood half an hour after the addition of the reagents. Since a pink color is distinctly visible in this reaction with one part of nitrogen in the form of nitrous acid in one thousand million parts of solution, it is safe to conclude that nitrous acid is not one of the products in this form of combustion.

To determine whether nitric acid is formed, after the combustion a portion of the sodic hydrate solution was neutralized, mixed with ferrous sulphate, and concentrated sulphuric acid poured beneath the solution. No color was visible at the junction of the two liquids. In a second test another portion of the alkaline solution was nearly neutralized with sulphuric acid, evaporated to dryness, and a few drops of phenolsulphuric acid added. Upon diluting to a definite volume, no difference could be perceived between the color of this solution and that given by phenolsulphuric acid alone in a blank experiment. In the combustion of sulphur oils in air, therefore, the atmospheric nitrogen is not affected.

For efficient aid in studying the details of these methods of analysis, I should acknowledge my obligations to Mr. W. O. Quayle, and to my assistants, Messrs D. B. Cleveland and G. M. Little.

II.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF HARVARD COLLEGE, UNDER THE DIRECTION OF PROFESSOR JOSIAH P. COOKE.

DOUBLE HALOID SALTS OF ANTIMONY, CALCIUM, AND MAGNESIUM, WITH OBSERVATIONS ON THE REMARKABLE DISSOCIATION OF

THESE COMPOUNDS.

BY FRANCIS GANO BENEDICT, A. M.

Presented by J. P. Cooke, May 9, 1894.

*

IN a recent paper, we described the results of our study of the double haloids of antimony and the alkaline metals. Since then we have extended the investigation to the corrresponding compounds with calcium and magnesium, and, although the work is still in an unfinished state, it must necessarily be interrupted for the present; and we therefore give here the results thus far obtained, the most important of which is the complete dissociation of a definite crystalline salt at the ordinary temperature of the air.

In the paper referred to,† a salt was mentioned having the composition SbCl,.2 KCl. 2 H2O, and the difficulties encountered in its preparation, analysis, and crystallographic study were discussed. Chief among these difficulties was the circumstance that the water of crystallization was lost wholly or in part at temperatures above -5° Cent., requiring the salt to be handled in a room below that temperature. In dealing with these new compounds the necessity for cold weather is even greater than in the case just mentioned. Hence the advancing of the season has prevented further work on this line. The research will be continued at the earliest opportunity.

Poggiale, in 1845, was the first investigator to obtain double haloids of antimony and the earthy alkaline metals: "Le chlorure de barium, uni au chlorure d'antimoine, présente une particularité qui

* These Proceedings, XXIX. 212.
↑ Loc. cit.

Comptes Rendus, XX. 1180.

mérite d'être mentionée. Si la solution de chlorure de barium n'est pas concentrée les deux sels séparent par le refroidissement; le chlorure de barium cristallise en tables, tandis que le protochlorure d'antimoine décompose l'eau. Il faut donc pour obtenir cette combinaison, concentrer la solution de chlorure de barium, avant d'y ajouter le protochlorure d'antimoine. La liqueur donne alors des aiguilles fines disposées en groupes étoilés. Ce sel double est composé de

SbCl,.2 BaCl + 5 HO.

Le protochlorure d'antimoine se combine également avec les chlorures de strontium, de calcium et de magnesium."

Schäffer, in 1860, working on the double iodides of antimony and the alkaline metals, described the double iodide of antimony and barium as a yellow salt with a formula,

Watts's Dictionary ‡ gives the formula alone of a salt of this class, i. e. 2 (BaCl,. SbCl2) 3 H2O.

Graham-Otto § makes the simple statement that antimonious chloride forms crystalline compounds with the chlorides of the alkaline and earthy alkaline metals.

Poggiale and Schäffer, therefore, appear to be the only investigators who succeeded in obtaining compounds with the earthy alkaline metals.

Although we have obtained a great many beautifully crystalline compounds from various mixtures of the haloids of antimony with the haloids of calcium, magnesium, barium, and strontium, only three of these have as yet been investigated. As has been before stated, cold weather is an absolute essential in the formation of the compounds, and the season is so far advanced that no more work can be done on them this year.

*Pogg. Ann., CIX. 611.

↑ Dictionary of Solubilities, p. 149.

Edition of 1888, Vol. I. p. 287.

§ Michaelis edition, Vol. II. p. 555.