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The Preparation of Oxygen. (Journ. de Pharm., 4th series, xiv. 22, 81, 131, 161.) Several accidents by explosion having occurred in the preparation of oxygen, and notably one at the Hotel Dieu, in February, 1870, when M. Dugue was much injured by the bursting of an iron bottle containing chlorate of potash and oxide of manganese, from which oxygen was being disengaged, a commission was appointed by the Society of Pharmacy at Paris to investigate the conditions necessary to be observed for a safe conduct of the process. This commission, composed of MM. Coulier, Limousin, J. Regnauld, Jungfleisch, and Baudrimont, has presented a full report on the subject. They consider the sources of danger in the preparation of oxygen by means of chlorate of potash to be the following :
1. The action of heat only on the chlorate of potash when the application is badly controlled.
2. The decomposition of the salt under the influence of oxides, when these are employed under bad conditions.
3. The energetic reactions which can arise from the association of the chlorate with certain substances accidentally mixed, and capable of acting upon it chemically.
They indicate that accidents may sometimes arise from the accidental admixture of carbon or sulphide of antimony with the oxide of manganese employed.
They recommend the use of an intimate mixture of equal parts of chlorate of potash and black oxide of manganese, which should be submitted to gentle heat in an iron retort, and the resulting gas washed with a solution of potash.
The following are the precautions which should be observed :
1. Never to employ the peroxide of manganese without first submitting it to calcination. This operation modifies the composition of the oxide (by reducing it to the state of red oxide, Mn, O.) but does not at all impair its activity. It offers the great advantage of destroying any combustible matters which may be accidentally present. It also chases out water, and decomposes any carbonate. This oxide of manganese loses none of its activity in the preparation of the oxygen, and may, therefore, be advantageously used over again, by simply washing out the chloride of potassium from the residue of the process, and drying the ide. In this way it will serve almost indefinitely.
2. To mix intimately the chlorate and the calcined oxide before introducing them into the retort; to employ the ingredients in equal parts. Such a mixture submitted to a sufficient temperature does not fuse, but disengages the gas with regularity.
3. To employ as gentle a heat as possible.
4. To ascertain the purity of the chlorate of potash, and to dry the salt. They draw particular attention to the danger which may result
the accidental substitution of sulphide of antimony or plumbago for the oxide of manganese.
In addition to this report presented by the commission, some of the members have individually published their researches on the subject. M. Ernest Baudrimont, in particular, has written a long memoir (pages 81, 161,) detailing a series of elaborate and exhaustive experiments. After a full history of our knowledge of the action of heat upon chlorate of potash, either alone or in contact with metallic oxides, he proceeds to give the results of his own investigations. Of the action of heat on chlorate of potash, he finds
1. That the chlorate enters into fusion at about 370°. 2. That it begins to decompose at about 400°.
3. That, raised quickly to a more elevated temperature, it dis.. engages tumultuously its oxygen with an evident final incandescence. Chlorate of potash is therefore an endothermic body, as demonstrated. by M. Berthelot.
The latter fact, relating to the disengagement of heat simultaneously with the liberation of oxygen, receives further confirmation in. other portions of his memoir. It is to be borne in mind that the decomposition of this salt requires a temperature more and more elevated in proportion as it loses its oxygen ; first, because the chloride of potassium which forms at the same time is less fusible than the salt generating it; secondly, because the perchlorate of potash formed is more difficult to fuse and to decompose than the chlorate.
Of the decomposition of chlorate of potash under the influence of the
presence of oxide of copper, the author finds :1. It can disengage its oxygen at 150 to 160 degrees lower than its normal temperature of decomposition (240° in place of 400°).
2. The disengagement of the gas takes place with great rapidity and extreme facility.
3. That at a given moment it occurs with emission of heat due only to the decomposition of the salt itself.
4. That it loses its oxygen with a little chlorine, and is totally converted into chloride of potassium.
5. That the oxide of copper is not in any way changed during this decomposition, preserving its initial weight and other properties.
M. Jungfleisch, on the contrary, maintains (p. 130) that the decomposition of chlorate of potash in the presence of metallic oxides is due to a chemical action, and not to any catalytic influence. He states that the oxides which are efficacious belong to those metals which form several compounds with oxygen. In the case of oxide of manganese, he conceives that permanganic acid is first formed, and finding no base with which it can combine, is again immediately decomposed; this action continuing until all the chlorate is decomposed.
Hyponitrous Acid as a Disinfectant. The members of a commission, appointed by the French Academy to investigate the relative merits of various disinfectants, agree that the first place among agents for attacking and destroying infectious germs must be accorded to hyponitrous acid. Extraordinary precautions must of course be observed in making use of this dangerous gas; the doors and windows must be carefully sealed with gummed paper when disinfecting a room containing 40 or 50 cubic yards. The materials are taken in the following proportions :-2 quarts of water, 31 pounds of ordinary commerical nitric acid, and pound of copper turnings or filings. A stoneware vessel is employed, holding two or three gallons. The exit doors are carefully pasted up, and the rooms left closed for forty-eight hours. The person opening the room at the expiration of the time should be protected in some way from breathing the gas by a suitable respirator.
Tests for Nitrous Acid. Thomas M. Chatard. (Chem. News, vol. xxiv., p. 225, from Amer. Journ, of Science.) During the course of some work on the nitrites of nickel and cobalt, it was necessary to have an easy and accurate test for nitrous acid. The author therefore reviewed all the tests given for that acid, comparing their relative degrees of delicacy, with the following results :-For testing, a very dilute solution of Fischer's salt
(CO, 6 NO, + 6 (K N 0,) + Ag)
which contained one 200,000th part, by weight, of nitrous acid, was employed.
Schönbein's * test with a weak solution of indigo decolourised by potassic sulphide failed to give accurate results. Besides, there are many substances which would have the same action upon the decolourised indigo as the nitrous acid.
C. D. Braun'st test with cobaltous chloride and potassic cyanide gave no reaction with so dilute a solution, even when several cubic centimetres were taken; the reaction only appearing when a comparatively strong solution of the nitrite was used.
Hadow's I reaction, in which a nitrite when heated with prussic acid, is detected by an alkaline sulphide, gave good results only when the nitrous acid was present in larger quantities, not being delicate enough to give a reaction with the standard solution of nitrite employed.
A modification of this' test suggested itself, in which the nitroprussic acid is thus produced. To the solution suspected of containing the acid, potassic ferrocyanide and acetic acid are added, and the whole boiled. The solution is allowed to cool, and ammonic sulphide added.
If nitrous acid was originally present, the characteristic blue reaction will appear. 10 c.c. of the test solution gave the reaction, but it failed with a smaller quantity.
The problem was finally solved by another reaction, namely, the production of phenol from aniline by means of nitrons acid. Evaporate the test liquid nearly to dryness, then rub it with a few drops of a strong solution of sulphate of aniline. If nitrous acid is present, the odour of phenol will immediately result. This test is remarkably delicate, 1 c.c. of the test solution giving a perfectly distinct reaction. Nor can nitrous be confounded with nitric acid, as this last produces no phenol, but merely a yellow colour, which of itself, as is well known, is of value as a test for that acid. On a New and very Delicate Test for Ammonia.
R. Böttger. (N. Repert. Pharm., xxi., 50. Journ. Chem. Soc., 2nd series, X., 263.) When to a solution containing the smallest quantity of ammonia, or of an ammoniacal salt, a few drops of a watery solution of carbolic acid are added, and then a little filtered solution of chloride of lime, the liquid becomes green, especially on warming.
The Strength of the Hydrocyanic Acid of Pharmacy. Dr. W. A. Tilden. (Pharm. Journ., 3rd series, ii., 81.) Having on several occasions noticed considerable deficiencies in the strength of hydrocyanic acid said to be B. P., that is represented as containing 2 per cent. of real acid, the author has examined a few samples, with the view of comparing them together, and of ascertaining how far they diverge from the Pharmacopoeial standard.
* Jahresberichte, 1864, 699. + Jahresberichte, 1865, 702. I Journ. Chem. Soc., vol. iv., p. 341.
A weighed quantity was in every case introduced into a stoppered bottle containing water, and more than sufficient potash to convert all the H C N into KCN. An accurately standardized solution of nitrate of silver was then run in from a burette, till, after shaking, the last drop produced a faint opacity of the fluid. As in most cases two experiments were performed with the sample, the close agreement of the results shows the accuracy of the method.
The first three are what they should be; the fourth is only threequarters of the strength required officially; the last four are quite unfit to use, and should be condemned.
Researches on the Physiological Properties of the Cyanates and on their Metamorphoses in the Animal Organism. MM. Rabuteau and Massul. (Journ. Pharm. Chim., 4th series, xv., 301.) The results of these experiments, in which the cyanates of potassium and sodium were employed, lead to the two following conclusions :-1. That these salts are not poisonous, as might have been expected. 2. That they give rise to alkaline carbonates as when the acetates, lactates, tartrates, etc., are administered. These carbonates are carried off for the most part in the urine.
Charcoal as an Antidote to Phosphorus. MM. Eulenberg and Voh). (Journ. Pharm. Chim., 4th series, xiv., 210.) It is well-known that several metallic salts, such as acetate of lead, sulphate of copper, the salts of mercury, of bismuth, etc., are withdrawn from their aqueous solutions by vegetable and especially by animal charcoal. Hitherto but little regard has been paid to this circumstance. But little application has been made of it except in chemical operations. It is also known that charcoal removes from