Another specimen, crystallised from benzene, remained constant in weight when heated for 11⁄2 hours at 90-100°, and was analysed. 0-1739 gave 0.5401 CO, and 0·1028 H2O. C=84·70; H=6·56. 0.6085 CO2 0.1147 H2O. C=84.28; H= 6·47.

0.1969 0.2558

9.6 c.c. moist nitrogen at 16° and 772 mm. N = 4.44. C23H19ON requires C=84·92; H=5·84; N=4·30 per cent.

The analytical results indicate that the substance contains oxygen, and that it is formed by the elimination of half the nitrogen from two mols. of ethyl-ß-naphthylamine (see p. 819).

It is very soluble in ethyl acetate or chloroform, and crystallises from its solution in either solvent in well defined, colourless prisms. When crystallised from alcohol and dried at the ordinary temperature, it contains 1 mol. of alcohol of crystallisation. An air-dried specimen gave the following numbers:

0-1403 gave 0.4154 CO, and 0.0910 H2O.

C=80·74; H=7.20. C23H19ON+C2HO requires C = 80-86; H=7-01 per cent.

The base, C23H19ON, when treated with acetic anhydride, benzoyl chloride (Schotten-Baumann method), or hydriodic acid and red phosphorus at 170° gives rise to resinous products.

The formation of a compound having the above constitution involves the elimination of ethylamine, and this base was identified in the following manner. The aqueous filtrate from the original precipitate was rendered alkaline, and distilled in a flask fitted with Kjeldahl bulbs, the ammoniacal gas evolved being passed into hydrochloric acid. On the addition of platinic chloride, an orange platinichloride was obtained which crystallised in hexagonal plates. On analysis:

0.3403 gave 0·1322 Pt. Pt=38.84.

(C2H, NH2)2,H,PtCl requires Pt=39.00 per cent.

5

Considerable progress has been made in the study of the action of benzaldehyde and its analogues on the alkyl and halogen derivatives of B-naphthylamine, and the results will be made known in a subsequent communication.

ROYAL COLLEGE OF SCIENCE, LONDON,

SOUTH KENSINGTON, S. W.

LXXV.-Estimation of Hypoiodites and Iodates and the Reaction of Iodine Monochloride with Alkalis.

By K. J. P. ORTON and W. L. BLACKMAN.

SEVERAL characteristic properties of solutions of hypoiodites have been recorded, that is, of solutions obtained by causing iodine (in the solid form or in solution) to react with solutions of alkalis.

The evolution of oxygen from hydrogen peroxide and barium peroxide, and the liberation of iodine from potassium iodide were noted by Schönbein (J. pr. Chem., 1861, 84, 385) and Seliwanow (Ber., 1894, 27, 1013); and the bleaching of indigo carmine and cochineal by Lunge and Schock (Ber., 1882, 15, 1883). The former reaction they attempted to apply quantitatively. Lonnes (Zeit. anal. Chem., 1894, 33, 409) found that sodium arsenite, and Péchard (Compt. rend., 1899, 128, 1453) that ferrous sulphate, were oxidised by these solutions.

The authors have used a modification of a method, proposed by Lonnes (loc. cit.), in which the oxidation of arsenite is employed to estimate the hypoiodite, the reaction being represented by the following equation:

MIO + H2ASO,

=

HASO4 + MI.

The iodate is estimated by acidifying the solution and titrating the iodine liberated by sodium sulphite or thiosulphate.

The solutions were prepared by mixing solutions of iodine in potassium iodide with alkalis, and from solutions of iodine monochloride in hydrochloric acid and alkalis. The reaction of iodine monochloride with alkalis is shown to be represented by the equation.

*

Initially, no potassium iodide is formed as in the reaction of iodine and alkalis. As the presence of potassium iodide has a disturbing effect, a greater excess of alkali is necessary before the reaction of iodine with starch or chloroform ceases (compare Lonnes and Péchard, loc. cit.). In our experiments, sufficient alkali was always present to ensure the absence of any free iodine. The solutions prepared resemble those obtained from iodine; they have a characteristic odour

A 3/10 to 4/10 N solution of iodine monochloride is easily made by gently warming 10 grams of iodine with a mixture of the calculated quantity (2·8 c.c.) of nitric acid of sp. gr. 1'4, and 30-40 c. c. of concentrated HCl of sp. gr. 115. When all the iodine has dissolved, the solution is diluted to 250 c.c. with water or dilute hydrochloric acid,

resembling that of iodoform or saffranine, and are pale straw-yellow. They oxidise arsenite, sulphite, and thiosulphate immediately. On standing, the hypoiodite disappears, and in most cases is not recognisable after 24 hours; ammonium hypoiodite, however, is much more stable and is not wholly decomposed after 2 weeks. When not too dilute, they give a precipitate of nitrogen iodide with ammonia. A trace of hypoiodite is readily recognisable, when no large quantity of alkali is present, by adding first sodium or potassium hydrogen carbonate and starch and finally potassium iodide. A blue colour immediately appears. If iodide is already present in quantity, the blue colour develops without the addition of potassium iodide (compare Taylor, this vol., 729).

Estimation of Hypoiodites and Iodate.

Excess of a standard solution of sodium arsenite is added to the alkaline hypoiodite. After standing for a short time, the alkali is removed by carbon dioxide,* and then the excess of arsenite estimated by standard iodine. Experiments have shown that under these circumstances the arsenite is not affected by iodate and iodide (compare Lonnes, loc. cit.). When ammonia is the alkali, it can be removed partly by boiling. The iodate is now estimated by adding a little dilute sulphuric acid, and titrating any iodine set free. A further quantity of sulphuric acid is added, and followed by addition of sulphite (or thiosulphate), and so on, until the solution is acid. This procedure avoids loss of iodine by the evolution of carbon dioxide, and further prevents the solution from ever becoming very acid, with the consequent interaction of the arsenate with the hydriodic acid. The following experiments show that this method is fairly trustworthy.

(1) To 100 c.c. of a solution containing 0.59 gram of potassium iodate and about 1 gram of potassium iodide, 10 c.c. of a 35 per cent. solution of potassium hydroxide were added, and then 26.6 c.c. of N/10 arsenious oxide. The solution was now saturated with carbon dioxide and allowed to stand 4 days. 26'6 c.c. N/10 iodine were required to oxidise the arsenite. The iodate was now estimated in an aliquot part. 0.5904 gram was found.

(2) 7·15 c.c. of N/10 arsenious oxide were added to a solution of ammonia (3) containing 0.1 gram of potassium iodate. After partial removal of the ammonia by boiling and conversion into carbonate by carbon dioxide, 7.15 c.c. N/10 iodine were required to oxidise the arsenite, and 0-1003 gram of potassium iodate was found.

Similar experiments gave equally satisfactory results. As a rule, the amount of iodate found is slightly in excess of that taken.

* Lonnes only used such dilute solutions of alkalis that this operation was not necessary.

Solutions of Potassium and Sodium Hydroxide.

To a 4 per cent. solution of potash, the solution of iodine monochloride in hydrochloric acid was cautiously added. At intervals, 100 c.c. of hypoiodite solution were withdrawn and titrated as above. The temperature during the experiment was not absolutely constant, but about 15°.

Estimated by distillation with ferric alum and sulphuric acid after conversion of the iodate into iodide by sulphurous acid, the total iodine 100 c.c. 24.05 c.c. of N/10 iodine, or 0.3054 gram.

per

In a similar experiment in which 20 c.c. of N/10 iodine in a solution of potassium iodide was added to 100 c.c. of 4 per cent. potassium hydroxide, 77 per cent. of the iodine was present as hypoiodite after 5 minutes, 31 per cent. after 20 minutes, 21.2 per cent. after 30 minutes, and 14 per cent. after 45 minutes.

Many series of analyses similar to the above were made, both with caustic potash and soda, giving the same results. After 24 hours, the whole of the hypoiodite had practically disappeared at the temperature of the laboratory (about 15°). Light had little effect on the rate of transformation. Two exactly similar solutions were made up together -one kept in darkness and the other in diffused daylight. Each was titrated every half-hour. After. 1 hours, 50 c.c. of one oxidised 3.86 c.c., and of the other 3.75 c.c. of N/10 arsenious oxide.

With solutions of potash less concentrated than 3 per cent., the whole of the iodine can be found as hypoiodite for a very short time, but with more concentrated solutions some conversion into iodate and iodide had always taken place before the arsenite was added. Thus 5 c.c. of an iodine monochloride solution were added to 75 c.c. of 3 per cent. aqueous potassium hydroxide, and excess of N/10 arsenious oxide immediately run in, but only 98-4 per cent. of the iodine was present as hypoiodite.

Solutions of Calcium and Barium Hydroxide.

The solutions were made up by adding the acid solution of iodine monochloride to saturated solutions of the alkalis, and also, according to Lunge and Schock's directions, by grinding up iodine with calcium

hydroxide and water, filtering, and making up to a given volume. The solutions obtained by each of these methods were titrated with arsenite and standard indigo. In the latter case, after addition of the indigo, the solution was allowed to stand for 15 minutes, and then the excess titrated with bleaching powder.

(1) N/25 calcium hydroxide solution. Total iodine per 100 c.c. = 1.92 c.c.

Percentage of iodine
as hypoiodite.

Temperature about 15°. of N/10 iodine, or 0.0244 gram.

Percentage of iodine c.c. of N/10 indigo

as iodate and iodide.

Time.

5 mins.

45

17 hours

bleached.

7.4

7.0

6.0

(2) A solution made by Lunge and Schock's method, and containing iodine = 5.65 c.c. of N/10 iodine per 100 c.c. (=0·0717 gram) after standing for 70 hours, did not oxidise arsenite, but bleached indigo. In two titrations, 100 c.c. bleached (a) 5'4 c.c., (b) 5'8 c.c. of N/10 indigo.

When iodine in potassium iodide is used, similar results are obtained. With iodine monochloride all the iodine has been found present as hypoiodite for a short time.

The transformation into iodate and iodide is considerably slower than with potassium hypoiodite. Thus, in 45 minutes, at about 15°, only 35 per cent. of hypoiodite has disappeared; while with potassium hypoiodite considerably more than 60 per cent. has disappeared in the same time. The indigo, bleached by a given solution, is seen to bear no relation to the arsenite oxidised, or, indeed, to the iodine present. The action on indigo decreases but little as the hypoiodite diminishes, and is considerable with solutions which do not act on arsenite. This action is due to the alkali alone. Thus, after adding indigo to 100 c.c. of calcium hydroxide solution, and estimating the former after 15 minutes standing, 5.3 c.c. of N/10 indigo had disappeared. The bleaching effect observed by Lunge and Schock in their solutions, which had stood for 24 hours, is therefore probably due to the alkali, and not to hypoiodite (compare Taylor, Trans., 1900, 77, 729).

Solutions of Ammonia and Methylamine.

In the case of ammonia, only dilute solutions could be obtained, owing to the precipitation of nitrogen iodide on further addition of iodine monochloride. Admixture of iodine monochloride and methylamine solution (3M) produces a yellow solution, and only after a considerable quantity of iodine monochloride has been added does a precipitate of methyldiiodoamine, CH, NI, appear. The alkaline

VOL. LXXVII.

3 M