XI.—Dinitro-benzol.
§ 247. Dinitro-benzol, C6H4(NO2)2 (ortho-, meta-, para-).—The ortho-compound is produced by the action of nitric acid on benzol, aided by heat in the absence of strong sulphuric acid to fix water. Some of the para-dinitro-benzol is at the same time produced. The meta-compound is obtained by the action of fuming nitric acid on nitro-benzol at a boiling temperature.
The physical properties of the three dinitro-benzols are briefly as follows:—
Ortho-d. is in the form of needles; m.p. 118°.
Meta-d. crystallises in plates; m.p. 90°.
Para-d. crystallises, like the ortho-compound, in needles, but the melting-point is much higher, 171° to 172°.
Just as nitro-benzol by reduction yields aniline, so do the nitro-benzols on reduction yield ortho-, meta-, or para-phenylene diamines.
Meta-phenylene diamine is an excellent test for nitrites; and, since the commercial varieties of dinitro-benzol either consist mainly or in part of meta-dinitro-benzol, the toxicological detection is fairly simple, and is based upon the conversion of the dinitro-benzol into meta-phenylene-diamine.
Dinitro-benzol is at present largely employed in the manufacture of explosives, such as roburite, sicherheit, and others. It has produced much illness among the workpeople in the manufactures, and amongst miners whose duty it has been to handle such explosives.
§ 248. Effects of Dinitro-benzol.—Huber[227] finds that if dinitro-benzol is given to frogs by the mouth in doses of from 100 to 200 mgrms., death takes place in a few hours. Doses of from 2·5 to 5 mgrms. cause general dulness and ultimately complete paralysis, and death in from one to six days.
[227] “Beiträge zur Giftwirkung des Dinitrobenzols,” A. Huber, Virchow’s Archiv, 1891, Bd. 126, S. 240.
Rabbits are killed by doses of 400 mgrms., in time varying from twenty-two hours to four days.
In a single experiment on a small dog, the weight of which was 5525 grms., the dog died in six hours after a dose of 600 mgrms.
It is therefore probable that a dose of 100 mgrms. per kilo would kill most warm-blooded animals.
A transient exposure to dinitro-benzol vapours in man causes serious symptoms; for instance, in one of Huber’s cases, a student of chemistry had been engaged for one hour and a half only in preparing dinitro-benzol, and soon afterwards his comrades remarked that his face was of a deep blue colour. On admission to hospital, on the evening of the same day, he complained of slight headache and sleeplessness; both cheeks, the lips, the muscles of the ear, the mucous membrane of the lips and cheeks, and even the tongue, were all of a more or less intense blue-grey colour. The pulse was dicrotic, 124; T. 37·2°. The next morning the pulse was slower, and by the third day the patient had recovered.
Excellent accounts of the effects of dinitro-benzol in roburite factories have been published by Dr. Ross[228] and Professor White,[229] of Wigan. Mr. Simeon Snell[230] has also published some most interesting cases of illness, cases which have been as completely investigated as possible. As an example of the symptoms produced, one of Mr. Snell’s cases may be here quoted.
[228] Medical Chronicle, 1889, 89.
[229] Practitioner, 1889, ii. 15.
[230] Brit. Med. Journ., March 3, 1894.
Diagram of Visual Field.
C. F. W., aged 38, consulted Mr. Snell for his defective sight on April 9, 1892. He had been a mixer at a factory for the manufacture of explosives. He was jaundiced, the conjunctiva yellow, and the lips blue. He was short of breath, and after the day’s work experienced aching of the forearms and legs and tingling of the fingers. The urine was black in colour, of sp. gr. 1024; it was examined spectroscopically by Mr. MacMunn, who reported the black colour as due neither to indican, nor to blood, nor bile, but to be caused by some pigment belonging to the aromatic series. The patient’s sight had been failing since the previous Christmas. Vision in the right eye was 6⁄24, left 6⁄36, both optic papillæ were somewhat pale. In each eye there was a central scotoma for red, and contraction of the field (see [diagram]). The man gradually gave up the work, and ultimately seems to have recovered. It is, however, interesting to note that, after having left the work for some weeks, he went back for a single day to the “mixing,” and was taken very ill, being insensible and delirious for five hours.
§ 249. The Blood in Nitro-benzol Poisoning.—The effect on the blood has been specially studied by Huber.[231] The blood of rabbits poisoned by dinitro-benzol is of a dark chocolate colour, and the microscope shows destruction of the red corpuscles; the amount of destruction may be gathered from the following:—the blood corpuscles of a rabbit before the experiment numbered 5,588,000 per cubic centimetre; a day after the experiment 4,856,000; a day later 1,004,000; on the third day the rabbit died.
[231] Op. cit.
In one rabbit, although the corpuscles sank to 1,416,000, yet recovery took place.
Dr. MacMunn[232] has examined specimens of blood from two of Mr. Snell’s patients; he found a distinct departure from the normal; the red corpuscles were smaller than usual, about 5 or 6 µ in diameter, and the appearances were like those seen in pernicious anæmia. Huber, in some of his experiments on animals, found a spectroscopic change in the blood, viz., certain absorption bands, one in the red between C and D, and two in the green between D and E; the action of reducing agents on this dinitro-benzol blood, as viewed in a spectroscope provided with a scale in which C = 48, D = 62, and E = 80·5, was as follows:—
[232] Op. cit.
| Dinitro-Bands. | |||
|---|---|---|---|
| In Red. | In Green. | ||
| 50-52 | 62-66 | 70-77 | |
| After NH4SO4, | 53-55 | 62-66 | 70-77 |
| Af„er NH3, | 54-58 | 60-65 | 70-77 |
| Af„er NH4SO4 + NH3, | 52-55 | 60-65 | 70-77 |
Taking the symptoms as a whole, there has been noted:—a blue colour of the lips, not unfrequently extending over the whole face, and even the conjunctivæ have been of a marked blue colour, giving the sufferer a strange livid appearance. In other cases there have been jaundice, the conjunctivæ and the skin generally being yellow, the lips blue. Occasionally gastric symptoms are present. Sleeplessness is common, and not unfrequently there is some want of muscular co-ordination, and the man staggers as if drunk. In more than one case there has been noticed sudden delirium. There is in chronic cases always more or less anæmia, and the urine is remarkable in its colour, which ranges from a slightly dark hue up to positive blackness. In a large proportion of cases there is ophthalmic trouble, the characteristics of which (according to Mr. Snell) are “failure of sight, often to a considerable degree, in a more or less equal extent on the two sides; concentric attraction of visual field with, in many cases, a central colour scotoma; enlargement of retinal vessels, especially the veins; some blurring, never extensive, of edges of disc, and a varying degree of pallor of its surface—the condition of retinal vessels spoken of being observed in workers with the dinitro-benzol, independently of complaints of defective sight. Cessation of work leads to recovery.”
§ 250. Detection of Dinitro-benzol.—Dinitro-benzol may be detected in urine, in blood, and in fluids generally, by the following process:—Place tinfoil in the fluid, and add hydrochloric acid to strong acidity, after allowing the hydrogen to be developed for at least an hour, make the fluid alkaline by caustic soda, and extract with ether in a separating tube; any metaphenylene-diamine will be contained in the ether; remove the ether into a flask, and distil it off; dissolve the residue in a little water.
Acidify a solution of sodium nitrite with dilute sulphuric acid; on adding the solution, if it contains metaphenylene-diamine, a yellow to red colour will be produced, from the formation of Bismarck brown (triamido-phenol).