after partial ignition. Of course if all is volatilized then no error is introduced into the experiment, but there may be some non-volatile material also transferred from the flasks. The total amount is so small that the error cannot be a large one.

5. Substances carried into the drying flasks by the stream of gas. Much care was taken to avoid error from this source. The main danger lay in the necessity for the use of some rubber connections. Vulcanized rubber was used. It was freed from excess of sulphur and was replaced by fresh pieces when attacked by the gas. The dry gas does not attack rubber very rapidly. Gaseous sulphur compounds, coming from the sulphuric acid, used in preparing and drying the hydrogen chloride, were probably carried through the drying flasks, but there seems to be no probability of their causing a decomposition of the oxychloride.

THE DETERMINATIONS.

All analyses which were completed under the proper conditions of the method, as already given, are here reported. Experiment III became contaminated from the iron support during the prolonged heating and came out consequently a little high, giving the ratio of ZrO, : ZrOC1,.3H2O as 53.12. In most of the subsequent analyses the ignition was carried out with the crucible suspended in a platinum wire cage from a glass support. Experiments VI and VIII were dried with an insufficient stream of gas, as already stated, and hence were partially decomposed. They gave 53.57 and 53.8, respectively. The remaining analyses follow:

Calculating these for the ratio ZrOC1,.3H,O: ZrO,, taking H= 1.008, O= 16, and Cl= 35.45. we have the following:

The atomic weight as determined by Bailey is 90.65. The mean value given in Clarke's Recalculation is 90.40. I purpose repeating the determinations with the oxychloride, with such modifications as have occurred to me since the completion of the above work.

UNIVERSITY OF NORTH CAROLINA.

THE SURFACE-TENSIONS OF AQUEOUS SOLUTIONS OF OXALIC, TARTARIC, AND CITRIC ACIDS.

BY C. E. LINEBARGER.
Received January 5, 1898.

N the determination of the surface-tensions of the solutions of citric, oxalic, and tartaric acids, the apparatus described in a previous number of this Journal' was employed. The "apparatus constant" was ascertained directly before and after a series of determinations, Ramsay and Shields'' data for water being taken as the standard; the variation, when there was one, which seldom happened, affected only the decimal places after the second. At least five readings of the adjustment of the tubes were made for every solution, and their average taken. The specific gravity of the solutions were determined to one or two figures in the fourth decimal place and were referred to water at temperature of its maximum density.

The thermometer had been tested by the Physikalische Reichsanstalt, at Berlin, and found to be without appreciable error in the neighborhood of 20°.

The acids were the purest obtainable and were recrystallized once or twice.

The solutions were prepared by dissolving the solid acids so as to form almost saturated solutions, and then diluting this stock solution; their surface-tensions were measured very soon after they were made up, although it was found that that phys1 This Journal, 18, 514.

2 Ztschr. phys. Chem., 12, 471. Surface-tension for water at 15° was taken to be 71.27 dynes per cm.

ical property did not alter with time, provided the solutions were hindered from evaporation; enough solutions to clearly determine the curve for each acid were investigated.

The percentage composition of the solutions were taken from the tables of specific gravities prepared by Gerlach.

The following tables contain the data which are represented graphically in Fig. 1; the curve for oxalic acid is raised a little

so as to make its origin coincide with the origin of the other curves; this slight shift has no appreciable influence on the shape of the curve.

SURFACE-TENSION OF OXALIC ACID SOLUTIONS AT 17.5°.

SURFACE-TENSION OF TARTARIC ACID SOLUTIONS AT 15°.

SURFACE-TENSION OF CITRIC ACID SOLUTIONS AT 15°.

The curves are quite different in trend. Oxalic and citric acids diminish in surface-tension as the concentration increases; the limited solubility of oxalic acid does not permit of an extended comparison of the two acids, however. A curious fact about the curve for citric acid is its being rectilinear and parallel to the x-axis at concentrations varying between thirty-five and sixty-five per cent.; within this range the surface-tensions of the solutions are independent of their concentrations.

The curve for tartaric acid gradually rises, becoming steeper and steeper as the concentration increases. For moderate concentrations it is approximately straight, which, for that matter, is the case with the other two acids also.

The reasons for the peculiarities of these curves are probably to be sought in the possible molecular polymerization and undoubted electrolytic dissociation of the acids in aqueous solution; very complicated relationships are presented, which in the absence of other physical data on the subject, it would now be unprofitable to attempt to unravel.

SODIUM PEROXIDE IN QUANTITATIVE ANALYSIS.'

W.

BY C. GLAser.
Received January 5, 1898.

HEMPEL' and J. Clark' first proposed to use sodium

peroxide in quantitative analysis. Hempel employed it for the oxidation of chromium, manganese, tungsten, and tin, and subsequent determination by known means; he also mentions that sulphur is completely oxidized to trioxide. He further recommends the reagent for the decomposition of zinc-blende and galena.

J. Clark recommends it for the estimation of sulphur, arsenic, and chromium, also for the separation of manganese from zinc, nickel, and cobalt. He states that the action of sodium peroxide on coke and coal is too violent for analytical purposes. T. Spüller and S. Kalman' use it on ferrochrome, chrome steel, 1 A review of various propositions made since 1892.

2 Ztschr. anorg. Chem., 1892, 3, 193-194.

8 J. Chem. Soc., 1893, 1079.

4 Ibid, 63, 1079.

b Chem. Zig., 17, 18.

Poleck' experimented on

chrome iron, and also sulphuretts.

organic substances, as did J. Tafel.'

In 1894, M. Hoehnel and C. Glaser3 made revised recommendations for the estimation of sulphur in pyrites. O. Kassner* states that iron is precipitated as hydroxide, but not changed into ferric acid, that, on the contrary, solutions of ferric acid are reduced by sodium peroxide. He gives detailed statements concerning separation of chromium and manganese; of the decomposition of freshly precipitated sulphides of antimony, tin, and arsenic. In 1895, L. Archbutt reports an analysis of sodium peroxide, showing the presence of nearly one-half of one per cent. of iron and alumina in the commercial article. Alb. Edinger' gives his experience in the determination of sulphur and chlorine in inorganic and organic combinations. M. C. Schuyler' proposed to determine mercury in mercuric salts by reduction to metal with sodium peroxide. In 1897 S. W. Parr" reports on the adaptability of sodium peroxide as a third group reagent in qualitative analysis, practically a review of the above-named publications, omitting quantitative features.

The Chemiker Zeitung contains a second note of the author, suggesting some improvements in the determination of sulphur in pyrites and later the same author1 separated iron from aluminum in phosphates and other minerals by means of sodium peroxide.

It may be in place here to state that the C. P. sodium peroxide of the trade has, as far as I have had occasion to test it, proved quite free from oxide of iron and alumina. It appears therefore probable that the article analyzed by Archbutt was a crude commercial product.

I cannot confirm O. Kassner's statement, that iron is not oxidized to ferric acid by sodium peroxide. If the reagent is added to a solution of an iron salt, without the precaution of

1 Chem. Ztg., 18, 103.

2 Ber. d. chem. Ges., 27, 816.

8 Arch. Pharm., 232, 222; Chem. Zig., 18, 1448.

4 Arch. Pharm., 232, 226.

5 Analyst, 20.

6 Ztschr. anal. Chem., 34, 362.

7 Chem. Ztg., 20, 1896.

8 This Journal, 19, 341.

9 Chem. Zig., 21, No. 6.

10 Ibid, 21, No. 69.