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hour, without vomiting or purging, or any convulsion. The shop-keeper sent word to her sister of what had happened, who came to her upon the message, and affirmed that it was not possible the cordial could have occasioned the death of the woman; and, to convince her of it, she filled out about three ounces and drank it. She continued talking, about two minutes longer, and was so earnest to persuade her of the liquor's being inoffensive, that she drank about two spoonfuls more, but was hardly seated in her chair when she died without the least groan or convulsion. A similar instance, fresh in the memory of every one, is that of Mr. Montgomery, who took one ounce and a half of this acid in Newgate, the night previous to his intended execution for forgery. The following is the method usually adopted by M. Vauquelin to obtain this acid pure:– o a quantity of powdered Prussian blue diffused in boiling water, let red nitric oxide of mercury be added till the blue color is destroyed. Filter the liquid, and concentrate by evaporation till a pellicle appears. On cooling, crystals of prussiate of mercury will be formed. Dry these, and put them into a tubulated glass retort, to the beak of which is adapted a horizontal tube about two feet long, and half an inch wide at its middle part. The first third part of the tube next the retort is filled with small pieces of white marble, the two other thirds with fused muriate of sime. To the end of this tube is adapted a small receiver, which should be artificially refrigerated. Pour on the crystals muriatic acid, in rather less quantity than is sufficient to saturate the oxide of mercury which formed them. Apply a very gentle heat to the retort. Prussic acid, named hydrocyanic by M. Gay Lussac, will be evolved in vapor, and will condense in the tube. Whatever muriatic acid may pass over with it will be abstracted by the marble, while the water will be absorbed by the muriate of lime. By means of a moderate heat applied to the tube, the prussic acid may be made to pass successively along; and, after being left some time in contact with the muriate of lime, it may be finally driven into the receiver. As the carbonic acid evolved from marble by the muriatic is apt to carry off some of the prussic acid, care should be taken to conduct the heat so as to prevent the distillation of this mineral acid. Prussic acid thus obtained has the following properties:–It is a colorless liquid, possessing a strong odor; and the exhalation, if incautiously snuffed up the nostrils, may produce sickness or fainting. Its taste is cooling at first, then hot, asthenic in a high degree, and it is a most deadly poison. Its specific gravity at 44}” is 0-7058; at 64° it is 0.6969. It boils at 81}*, and congeals at about 3°. It then crystallises regularly, and affects sometimes the fibrous form of nitrate of ammonia. The cold which it produces, when reduced into vapor, even at the temperature of 68°, is sufficient to congeal it. M. Gay Lussac analysed this acid by introducing its vapor at the temperature of 86° into a jar, o filled with oxygen, over warm mercury. When the temperature of the mer

cury was reduced to that of the surrounding atmosphere, a determinate volume of the gaseous mixture was taken and washed in a solution of o which abstracts the prussic acid, and eaves the oxygen. A known volume was introduced into a Volta's eudiometer, with platina wires, and an electric spark was passed across the gaseous mixture. The combustion is lively, and of a bluish-white color. A white prussic vapor is seen, and a diminution of volume takes place, which is ascertained by measuring the residue in a graduated tube. This, being washed with a solution of potash or barytes, suffers a new diminution from the absorption of carbonic acid gas formed. Lastly, the gas which the alkali has left is analysed over water by hydrogen, and it is ascertained to be a mixture of nitrogen and oxygen. The following are the results referred to prus

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This acid, when compared with the other animal products, is distinguished by the great quantity of nitrogen it contains, by its small quantity of hydrogen, and especially by the absence of oxygen.

When this acid is kept in well-closed vessels, even though no air be present, it is sometimes decomposed in less than an hour; though it has been occasionally kept for fifteen days without alteration. It begins by assuming a reddishbrown color, which becomes deeper and deeper, and it gradually deposits a considerable carbonaceous matter, which gives a deep color to both water and acids, and emits a strong smell of ammonia. If the bottle containing the prussic acid be not hermetically sealed nothing remains but a dry charry mass, which gives no color to water. Thus a prussiate of ammonia is formed at the expense of a part of the acid, and an azoturet of carbon. When potassium is heated in prussic acid vapor mixed with hydrogen or

nitrogen, there is absorption without inflammation, and the metal is converted into a gray spongy substance, which melts, and assumes a yellow color. Supposing the quantity of potassium employed capable of disengaging from water a volume of hydrogen equal to fifty parts, we find after the action of the potassium, 1. That the gaseous mixture has experienced a diminution of volume amounting to fifty parts: 2. On treating this mixture with potash, and analysing the residue by oxygen, that fifty parts of hydrogen have been produced: 3. And consequently that the potassium has absorbed 100 parts of prussic vapor; $or there is a diminution of fifty parts, which would obviously have been twice as great, had not fifty parts of hydrogen been disengaged. The yellow matter is prussiate of potash; pro}. a prusside of potassium, analogous in its rmation to the chloride and iodide, when muriatic and hydriodic gases are made to act on potassium. The base of prussic acid, thus divested of its acidifying hydrogen, should be called, agreeably to the same chemical analogy, prussine. M. Gay Lussac styles it cyanogen, because it is the principle which generates blue. The prusside or cyanide of potassium gives a very alkaline solution in water, even when a great excess of hydrocyanic vapor has been present at its formation. In this respect it differs from the chlorides and iodides of that metal, which are perfectly neutral. On subjecting prussic acid to the action of a galvanic battery, much hydrogen is disengaged at the negative pole; and prussine or cyanogen at the positive, which remains dissolved in the acid. is compound should be regarded as a hypoprussic or prussous acid. Since potash b heat separates the hydrogen of the prussic acid, we see that in exposing a mixture of potash and animal matters to a high temperature, a true prusside or cyanide of potash is obtained, formerly called the Prussian or phlogisticated alkali. When prusside of potassium is dissolved in water, prussiate of potash is produced, which is decomposed by the acids without generating ammonia or carbonic acid; but, when prusside of potash dissolves in water, no change takes !. and neither ammonia, carbonic acid, nor ydrocyanic vapor is given out, unless an acid be added. These are the characters which distinguish a metallic prusside or cyanide from the cyanide of an oxide. From the experiments of M. Magendie it appears that the pure prussic acid is the most violent of all poisons. When a rod dipped into it is brought in contact with the tongue of an animal, death ensues before the rod can be withdrawn. If a bird be held a moment over the mouth of a phial containing this acid, it dies. A French professor of chemistry left by accident, on a table, a flask containing alcohol impregnated with prussic acid; the servant, enticed by the agreeable flavor of the liquid, swallowed a small glass of it. In two minutes she dropt down dead, as if struck with apoplexy. ‘Scharinger, a professor at Vienna,' says Orfila, “prepared a pure and concentrated prus

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And, mixing the ingredients well together, he administers a table-spoonful every morning and evening. A well written report of the use of the prussic acid in certain diseases, by Dr. Magendie, was communicated by Dr. Granville to Mr. Brande, and is inserted in the fourth volume of the Journal of Science. For the following ingenious and accurate process, for preparing prussic acid for medicinal uses, we are indebted to Dr. Nimmo of GlasOW :‘Take of the ferroprussiate of potash 100 grains, of the protosulphate of iron eighty-four grains and a half; dissolve them separately in four ounces of water, and mingle them. After allowing the precipitate of the protoprussiate of iron to settle, pour off the clear part, and add water to wash the sulphate of potash completely away. To the protoprussiate of iron, mixed with four ounces of pure water, add 135 grains of the peroxide of mercury, and boil the whole till the oxide is dissolved. With the above proportions of peroxide of mercury, the protoprussiate of iron is completely decomposed. The vessel being kept warm, the oxide of iron will fall to the bottom; the clear part may be poured off to be filtered through paper, taking care to keep the funnel covered, so that crystals may not form in it by refrigeration. The residuum may be treated with more water, and thrown upon the filter, upon which warm water ought to be poured, until all the soluble part is washed away. By evaporation, and subsequent rest in a cool place, 145 grains of crystals of the prusside or cyanide of mercury will be procured in quadrangular prisms. “The following is a new process for obtaining the prussic acid:—Take of the prusside of mercury in fine powder one ounce, diffuse it in two ounces of water, and to it, by slow degrees, add a solution of hydrosulphuret of barytes, made by decomposing sulphate of barytes with charcoal in the common way. Of the sulphuret of barytes take an ounce, boil it with six ounces of water, and filter it as hot as possible. Add this in small portions to the prusside of mercury, agitating l. whole very well, and allowing sufficient time for the prusside to dissolve, while the decomposition is going on between it and the hydrosulphuret as it is added. Continue the addition of the hydrosulphuret so long as a dark precipitate of sulphuret of mercury falls down, and even allowing a small excess. Let the whole be thrown upon a filter, and kept warm till the fluid drops through; add more water to wash the sulphuret of mercury, until eight ounces of fluid have passed through the filter, and it has become tasteless. To this fluid, which contains the prussiate of barytes, with a small excess of hydrosulphuret of barytes, add sulphuric acid, diouted with an equal weight of water, and allowed to become cold, so long as sulo ate of barytes falls down. The excess of sulphureted hydrogen will be removed by adding a sufficient portion of carbonate of lead, and agitating very well. The whole may now be put upon a filter, which must be closely covered; the fluid which passes is the hydrocyanic or prussic acid, of what is called the medical standard strength.’ Dr. Nimmo finds that prussiue of mercury is capable of dissolving the mercurial peroxide. Hence the above proportions must be strictly observed, if we wish to obtain this powerful medicine of uniform strength. He conceives, therefore, that the ferroprussiate of potash should be taken for the basis of the calculation. Scheele found that prussic acid occasioned precipitates with only the following three inetallic solutions; nitrates of silver, and mercury, and carbonate of silver. The first is white, the second black, the third green, becoming blue. The prussiates or hydrocyanates are all alkaline, even when a great excess of acid is employed in their formation; and they are decomposed by the weakest acids. The hydrocyanate of ammonia crystallises in cubes, in small prisms crossing each other, or in feathery crystals, like the leaves of a fern. Its volatility is such that at the temperature of 71 \o it is capable of bearing a pressure of 1772 inches of mercury; and at 97° its elasticity is equal to that of the atmosphere. Its great volatility prevented M. Gay Lussac from determining the proportion of its constituents. M. Gay Lussac considers Prussian blue as a hydrated prusside of iron, or a cyanide having water in combination ; and M. Vauquelin, in a memoir lately read before the Academy of Sciences, regards Prussian blue as a simple hydrocyanate of iron. He finds that water impregnated with russine can dissolve iron without changing it into Prussian blue, and without the disengagement of any hydrogen gas, while Prussian blue was left in the undissolved portion. But prussic acid converts iron or its oxide into Prussian blue without the help either of alkalis or acids. He farther lays it down as a general rule, that those metals which, like iron, decompose water at the ordinary temperature of the atmosphere, form hydrocyanates; and that those metals which do not possess this power, as silver and quicksilver, form only cyanides. Prussic acid is easily separated from potash by carbonic acid, but, when oxide of iron is added to the compound, a triple salt is formed, usually called ferroprussiate of potash. The method of preparing this salt practised by Klaproth is one of the best. It is as follows:—Prepare pure potass, by gradually projecting into a large crucible, heated to whiteness, a mixture of equal parts of purified nitre and crystals of tartar; when the whole is injected, let it be kept at a white heat for half an hour, to burn off the coal. Detach the alkali thus obtained from the

crucible, reduce it to powder, spread it on a muffle, and expose it to a white heat for half an hour. Dissolve it in six times its weight of water, and filter the solution while warm. Pour this solution into a glass receiver, placed in a sand furnace, heated to 170° or 180°, and then gradually add the best Prussian blue in powder, injecting new portions of it as the former becomes gray, and supplying water as fast as it evaporates; continue, until the added portions are no longer discolored; then increase the heat to 212°, and continue for half an hour. Filter the ley thus obtained, and saturate it with sulphuric acid moderately diluted; a precipitate will appear: when this ceases, filter off the whole, and wash the precipitate. Evaporate the filtered liquor to about one quarter, and set it by to crystallise: after a few days, yellowish crystals of a cubic or quadrangular form will be found mixed with some sulphate of potass and oxide of iron; pick out the yellowish crystals, lay them on blotting paper, and redissolve them in four times their weight of cold water, to exclude the sulphate of potass. Essay a few drops of this solution with a solution of barytes, to see whether it contains any sulphuric acid: filter off the solution from

the sulphat of barytes, which will have precipi

tated, and set it by to crystallise for a few days, that the barytes, if any should remain, may be precipitated. If the crystals now obtained be of a pale yellow color, and discover no bluish streaks, when sprinkled over with muriatic acid, they are fit for use, and should be kept in a well stopped bottle, which, to preserve them from the air, should be filled with alcohol, as they are insoluble in it. M. Gay Lussac prepared a hydrocyanate of potash and silver, which was quite neutral, and which crystallised in hexagonal plates. The solution of these crystals precipitates salts of iron and copper, white. Muriate of ammonia does not render it turbid; but muriatic acid, by disengaging hydrocyanic acid, precipitates chloride of silver. Sulphureted hydrogen produces in it an analogous change. This compound, says M. Gay Lussac, is evidently the triple prussiate of potash and silver; and its formation ought to be analogous to that of the other triple hydrocyanates. “And as we cannot doubt,’ adds he, “that hydrocyanate of potash and silver is in reality, from the mode ..". formation, a compound of cyanide of silver and hydrocyanate of potash, I conceive that the hydrocyanate of potash and iron is likewise a compound of neutral hydrocyanate of potash, and subcyanide of iron, which I believe to be combined with hydrocyanic acid in the white precipitate. We may obtain it perfectly neutral, and then it does not decompose alum; but the hydrocyanate of potash, which is always alkaline, produces in it a light and flocculent precipitate of alumina. To the same excess of alkali we must ascribe the ochry color of the precipitates which hydrocyanate of potash forms with the persalts of iron.” M. Vauquelin has given the following very elegant process for obtaining pure hydrocyanic or prussic acid, from the cyanide or prusside of mercury:Considering that mercury has a strong attraction for sulphur, and that prussine unites easily to hydrogen, when presented in the proper state,

he thought that sulphureted hydrogen might be

employed for decomposing dry cyanide(prusside) of mercury. He operated in the following way: —He made a current of sulphureted hydrogen gas, disengaged slowly from a mixture of sulphuret of iron, and very dilute sulphuric acid, pass slowly through a glass tube slightly heated, filled with the mercurial prusside, and commucating with a receiver, cooled by a mixture of salt and snow. As soon as the sulphureted hydrogen came in contact with the mercurial salt, this last substance blackened, and this effect gradually extended to the farthest extremity of the apparatus. During this time no trace of sulphureted hydrogen could be perceived at the mouth of a tube proceeding from the receiver. As soon as the odor of this gas began to be perceived, the process was stopped; and the tube was heated in order to drive over the acid which might still remain in it. The apparatus being unluted, he found in the receiver a colorless fluid, which possessed all the known properties of prussic acid. It amounted to nearly the fifth part of the prusside of mercury employed. This process is easier, and furnishes more acid, than M. Gay Lussac's, by means of muriatic acid. He repeated it several times, and always successfully. It is necessary merely to take care to stop the process before the odor of the sulphureted hydrogen begins to be perceived, otherwise the hydrocyanic acid will be mixed with it. However, we may avoid this inconvenience by placing a little carbonate of lead at the extremity of the tube. As absolute hydrocyanic acid is required only for chemical researches, and as it cannot be employed in medicine, it may be worth while, says M. Vauquelin, to bring to the recollection of apothecaries a process of M. Proust, which has perhaps escaped their attention. It consists in passing a current of sulphureted hydrogen gas through a cold saturated solution of prussiate of mercury in water, till the liquid contains an excess of it; to put the mixture into a bottle, in order to agitate it from time to time; and finally, to filter it. If this prussic acid, as almost always happens, contains traces of sulphureted hydrogen, agitate it with a little carbonate of lead, and filter it again. By this process we may obtain hydrocyanic acid in a much greater degree of concentration than is necessary for medicine. It has the advantage over the dry prussic acid, of being capable of being preserved a long time, always taking care to keep it as much as possible from the contact of air and heat. Dr. Nimmo's directions for preparing the prusside of mercury ought to be attended to. PRUSSINE, or PRussic Gas, in chemistry, the cyanogen of M. Gay Lussac, is a peculiar gas obtained by decomposing prusside of mercury by heat. The term cyanogen signifies the produce of blue; but as the production of blue is never the result of the direct action of this substance on any other single body, but an indirect and unexplained operation of it in conjunction with iron, hydrogen, and oxygen, the

same reason which leads to the term cyanogen, would warrant us in calling it leucogen, erythrogen, or chlorogen; for it produces, white, red, or green, with other metals, as it produces blue with iron. By digesting red oxide of mercury with prussian blue and hot water, we obtain a prusside perfectly neutral, which crystallises in long foursided prisms, truncated obliquely. By repeated solutions and crystallisations, we may free it from a small portion of adhering iron. But M. Gay Lussac prefers boiling it with red oxide of mercury, which completely precipitates the oxide of iron, and he then saturates the excess of oxide of mercury with a little prussic acid, or a little muriatic acid. The prusside thus formed is decomposed by heat to obtain the radical. For common experiments we may dispense with these precautions. When this cyanide is boiled, with red oxide of mercury, it dissolves a considerable quantity of the oxide, becomes alkaline, crystallises no longer in prisms, but in small scales, and its solubility in water appears a little increased. When evaporated to dryness, it is very easily charred, which obliges us to employ a water bath. This compound was observed by M. Proust. When decomposed by heat, it gives abundance of prussine, but mixed with carbonic acid gas. Proust says that it yields ammonia, oil in considerable abundance, carbonic acid, azote, and oxide of carbon. He employed a moist prusside. Had it been dry, the discovery of prussine could hardly have escaped him. The prusside of mercury, when neutral and quite dry, gives nothing but prussine; when moist, it furnishes only carbonic acid, ammonia, and a great deal of prussic acid vapor. When we employ the prusside made with excess of peroxide, the same products are obtained, but in different proportions, along with azote, and a brown liquid, which Proust took for an oil, though it is not one in reality. Hence, to obtain pure prussine, we must employ the neutral prusside in a state of perfect dryness. The other mercurial compound is not, however, . a sub-prusside. It is a compound of oxide of mercury and the prusside. When the simple mercurial prusside is exposed to heat in a small glass retort, or tube, shut at one extremity, it soon begins to blacken. It appears to melt like an animal matter, and then the prussine is disengaged in abundance. This gas is pure from the beginning of the process to the end, provided always that the heat be not very high; for, if it were sufficiently intense to melt the glass, a little azote would be evolved. Mercury is volatilised with a considerable quantity of prusside, and there remains a charry matter of the color of soot, and as light as lampblack. The prusside of silver gives out likewise prussine when heated ; but the mercurial prusside is preferable to every other. Prussine or cyanogen is a permanently elastic fluid. Its smell, which it is impossible to describe, is very strong and penetrating. Its solution in water has a very sharp taste. The gas burns with a bluish flame mixed with purple. Its specific gravity, compared to that of air, is 18064. M. Gay Lussac obtained it by weigh

ing at the same temperature, and under the same F. a balloon of about two litres and a alf (152-56 cubic inches), in which the vacuum was made to the same degree, and alternately full of air and prussine. 100 cubic inches weigh therefore 55:1295 grains. Prussine is capable of sustaining a pretty high heat, without being decomposed. Water, with which M. Gay Lussac agitated it for some minutes, at the temperature of 68°, absorbed about four times and a half its volume. Pure alcohol absorbs twenty-three times its volume. Sulhuric ether and oil of turpentine dissolve at east as much as water. Tincture of litmus is reddened by prussine. On heating the solution the gas is disengaged, mixed with a little carbonic acid, and the blue color of the litmus is restored. The carbonic acid proceeds no doubt from the decomposition of a small quantity of prussine and water. It deprives the red sulphate of manganese of its color, a property which prussic acid does not possess. This is a proof that its elements have more mobility than those of the acid. In the dry way it separates the carbonic acid from the carbonates. Phosphorus, sulphur, and iodine, may be sublimed by the heat of a spirit-lamp in prussine, without occasioning any change on it. Its mixture with hydrogen was not altered by the same temperature, or by passing electrical sparks through it. Copper and gold do not combine with it; but iron, when heated almost to whiteness, decomposes it in part. The metal is covered with a slight coating of charcoal, and becomes brittle. The undecomposed portion of the gas is mixed with azote (contains free azote). In one trial the azote constituted 0-44 of the mixture, but in general it was less. Platinum, which had been placed beside the iron, did not undergo any alteration. Neither its surface, nor that of the tube, was covered with charcoal like the iron. In the cold, potassium acts but slowly on russine, because a crust is formed on its surace, which presents an obstacle to the mutual action. On applying the spirit-lamp, the potassium becomes speedily incandescent; the absorption of the gas begins, the inflamed disc gradually diminishes, and when it disappears entirely, which takes place in a few seconds, the absorption is likewise at an end. Supposing we employ a quantity of potassium that would disengage fifty parts of hydrogen from water, we find that from forty-eight to fifty parts of gas have disappeared. On treating the residue with potash, there usually remains four or five parts of hydrogen, sometimes ten or twelve. M. Gay Lussac made a great number of experiments to discover the origin of this gas. He thinks that it is derived from the water which the prusside of mercury contains when it has not been sufficiently dried. Prussic acid vapor is then produced, which, when decomposed by the potassium, leaves half its volume of hydrogen. Potassium, therefore, absorbs a volume of pure prussine, equal to that of the hydrogen which it would disengage from water. The compound of prussine and potassium is yellowish. It dissolves in water without effer

vescence, and the solution is strongly alkaline. Its taste is the same as that of hydrocyanate or simple prussiate of potash, of which it possesses all the properties. The gas being very inflammable, M. Gay Lussac exploded it in Volta's eudiometer, with about twice and a half its volume of oxygen. The detonation is very strong; and the flame is bluish, like that of sulphur burning in oxygen. It is now obvious that the action of potassium on prussine agrees with its action on prussic acid. We have seen that it absorbs fifty parts of the first, and likewise that it absorbs 100 parts of the second, from which it separates fifty parts of hydrogen. But 100 parts of prussic acid vapor, minus fifty parts of hydrogen, amount exactly to fifty parts prussine. Hence the two results agree perfectly, and the two compounds obtained ought to be identical, which agrees precisely with experiment. The analysis of prussine being of great imortance, M. Gay Lussac attempted it likewise y other methods. Having put prusside of mercury into the bottom of a glass tube, he covered it with brown oxide of copper, and then raised the heat to a dull red. On heating gradually the part of the tube containing the prusside, the prussine was gradually disengaged, and passed through the oxide, which it reduced completely to the metallic state. On washing the gaseous products with aqueous potash, at different parts of the process, he obtained only from 0-19 to 0.30 of azote, instead of 0.33, which ought to have remained according to the preceding analysis. Presuming that some nitrous compound had been formed, he repeated the experiment, covering the oxide with a column of copper filings, which he kept at the same temperature as the oxide. With this new arrangement, the results were very singular; for the smallest quantity of azote which he obtained during the whole course of the experiment was 32-7 for 100 of gas, and the greatest was 34°4. The mean of all the trials was, Azote . . . 33.6 or nearly 1 Carbonic acid . 66.4 2 A result which shows clearly that P. Contains two volumes of the vapor of carbon, and one volume of azote. In another experiment, instead of passing the prussine through the oxide of copper, he made a mixture of one part of the prusside of mercury, and ten parts of the red oxide, and after introducing it into a glass tube, close at one end, he covered it with copper filings, which he raised first to a red heat. On heating the mixture successively, the decomposition went on with the greatest facility. The proportions of the gaseous mixture were less regular than in the preceding experiment. Their mean was, Azote . 34-6 instead of 33-3 Carbonic acid 65.4 66-6 In another experiment he obtained,— Azote 32-2 Carbonic acid . 67-8 Now the mean of these results gives,— Azote . . . 33.4 Carbonic acid . 66-6

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