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hour, without vomiting or purging, or any con cury was reduced to that of the surrounding vulsion. The shop-keeper sent word to her atmosphere, a determinate volume of the gaseous sister of what had happened, who came to her mixture was taken and washed in a solution of upon the message, and affirmed that it was not potash, which abstracts the prussic acid, and possible the cordial could have occasioned the leaves the oxygen. A known volume was introdeath of the woman; and, to convince her of it, duced into a Volta's eudiometer, with platina she filled out about three ounces and drank it. She wires, and an electric spark was passed across continued talking, about two minutes longer, the gaseous mixture. The combustion is lively, and was so earnest to persuade her of the and of a bluish-white color. A white prussic liquor's being inoffensive, that she drank about vapor is seen, and a diminution of volume takes two spoonfuls more, but was hardly seated in place, which is ascertained by measuring the her chair when she died without the least groan residue in a graduated tube. This, being washed or convulsion. A similar instance, fresh in the with a solution of potash or barytes, suffers a memory of every one, is that of Mr. Montgo- new diminution from the absorption of carbonic mery, who took one ounce and a half of this acid acid gas formed. Lastly, the gas which the in Newgate, the night previous to his intended alkali has left is analysed over water by hydrogen, execution for forgery.

and it is ascertained to be a mixture of nitrogen The following is the method usually adopted and oxygen. by M. Vauquelin to obtain this acid pure : The following are the results referred to prusTo a quantity of powdered Prussian blue 'sic acid vapor: diffused in boiling water, let red nitric oxide

Vapor

100 of mercury be added till the blue color is

Diminution after combustion

78.5 destroyed. Filter the liquid, and concentrate Carbonic acid gas produced 101.0 by evaporation till a pellicle appears. On cool

Nitrogen

46.0 ing, crystals of prussiate of mercury will be

Hydrogen

55.0 formed. Dry these, and put them into a tubulated glass retort, to the beak of which is During the combustion a quantity of oxygen adapted a horizontal tube about two feet long, disappears, equal to about one and a quarter of and half an inch wide at its middle part. The the vapor employed. first third part of the tube next the retort is filled M. Gay Lussac also analysed prussic acid by with small pieces of white marble, the two other passing its vapor through an ignited porcelain thirds with fused muriate of lime. To the end tube containing a coil of fine iron wire, which of this tube is adapted a small receiver, which facilitates the decomposition of this vapor, as it should be artificially refrigerated. Pour on the does with ammonia. No trace of oxygen could crystals muriatic acid, in rather less quantity be found in prussic acid. And again, by transthán is sufficient to saturate the oxide of mer- mitting the acid in vapor over ignited peroxide cury which formed them. Apply a very gentle of copper in a porcelain tube, he came to the heat to the retort. Prussic acid, named hydro-, same conclusion : cyanic by M. Gay Lussac, will be evolved in

One volume of the vapor of carbon, vapor, and will condense in the tube. What

Half a volume of hydrogen, ever muriatic acid may pass over with it will be abstracted by the marble, while the water will condensed into one volume; or in weight,

Half a volume of nitrogen, be absorbed by the muriate of lime. By means

Carbon

44.39 of a moderate heat applied to the tube, the prus

Nitrogen

51.71 sic acid may be made to pass successively along;

3.90 and, after being left some time in contact with

Hydrogen the muriate of lime, it may be finally driven into

100.00 the receiver. As the carbonic acid evolved from marble by the muriatic is apt to carry off some This acid, when compared with the other of the prussic acid, care should be taken to con- animal products, is distinguished by the great duct the heat so as to prevent the distillation of quantity of nitrogen it contains, by its small this mineral acid.

quantity of hydrogen, and especially by the Prussic acid thus obtained has the following absence of oxygen. properties :—It is a colorless liquid, possessing When this acid is kept in well-closed vessels, a strong odor; and the exhalation, if incautious- even though no air be present, it is sometimes ly snuffed up the nostrils, may produce sickness decomposed in less than an hour; though it has or fainting. Its taste is cooling at first, then been occasionally kept for fifteen days without hot, asthenic in a high degree, and it is a most alteration. It begins by assuming a reddishdeadly poison. Its specific gravity at 441° is brown color, wnich becomes deeper and deeper, 0.7058; at 64o it is 0:6969. It Þoils at 811', and it gradually deposits a considerable carbonaand congeals at about 3o. It then crystallises ceous matter, which gives a deep color to both regularly, and affects sometimes the fibrous form water and acids, and emits a strong smell of of nitrate of ammonia. The cold which it pro- ammonia. If the bottle containing the prussic duces, when reduced into vapor, even at the acid be not hermetically sealed nothing remains temperature of 68°, is sufficient to congeal it. but a dry charry mass, which gives no color to

M. Gay Lussac analysed this acid by intro. water. Thus a prussiate of ammonią is formed ducing its vapor at the temperature of 86° into a at the expense of a part of the acid, and an jar, two-thirds filled with oxygen, over warm azoturet of carbon. When potassium is heated mercury. When the temperature of the mer- in prussic acid vapor mixed with hydrogen or

Pure sugar

ritrogen, there is absorption without inflamma- sic acid ; he spread a certain quantity of it on tion, and the metal is converted into a gray his naked arm, and died a little time thereafter.' spongy substance, which melts, and assumes a Dr. Magendie has, however, ventured to inyellow color.

troduce its employment into medicine. He Supposing the quantity of potassium employ- found it beneficial against phthisis and chronic ed capable of disengaging from water a volume catarrhs. His formula is the following :of hydrogen equal to fifty parts, we find after the Mix one part of the pure prussicor hydrocyanic action of the potassium, 1. That the gaseous acid of M. Gay Lussac with eight and a half of mixture has experienced a diminution of volume water by weight. To this mixture he gives the amounting to fifty parts : 2. On treating this name of medicinal prussic acid. mixture with potash, and analysing the residue

Of this he takes 1 gros. or by oxygen, that fifty parts of hydrogen have been

59 gr. Troy Distilled water

1 lb.

or 7560 grs. produced : 3. And consequently that the potassium has absorbed 100 parts of prussic vapor;

1} ox. or 708% grs. Sor there is a diminution of fifty parts, which And, mixing the ingredients well together, he Kould obviously have been twice as great, had administers a table-spoonful every morning and not fifty parts of hydrogen been disengaged. evening. A well written report of the use of the The yellow matter is prussiate of potash; pro- prussic acid in certain diseases, by Dr. Magendie, perly a prusside of potassium, analogous in its was communicated by Dr. Granville to Mr. formation to the chloride and iodide, when Brande, and is inserted in the fourth volume of muriatic and hydriodic gases are made to act on the Journal of Science. potassium.

For the following ingenious and accurate proThe base of prussic acid, thus divested of its cess, for preparing prussic acid for medicinal acidifying hydrogen, should be called, agreeably uses, we are indebted to Dr. Nimmo of Glasto the same chemical analogy, prussine. M. gow :Gay Lussac styles it cyanogen, because it is the * Take of the ferroprussiate of pocash 100 principle which generates blue.

grains, of the protosulphate of iron eighty-four The prusside or cyanide of potassium gives a grains and a half; dissolve them separately in very alkaline solution in water, even when a four ounces of water, and mingle them. After great excess of hydrocyanic vapor has been pre- allowing the precipitate of the protoprussiate of sent at its formation. In this respect it differs iron to settle, pour off the clear part

, and add from the chlorides and iodides of that metal, water to wash the sulphate of potash completely which are perfectly neutral.

away. To the protoprussiate of iron, mixed On subjecting prussic acid to the action of a with four ounces of pure water, add 135 grains galvanic battery, much hydrogen is disengaged of the peroxide of mercury, and boil the whole at the negative pole; and prussine or cyanogen till the oxide is dissolved. With the above proat the positive, which remains dissolved in the portions of peroxide of mercury, the protoprusacid. This compound should be regarded as a siate of iron is completely decomposed. The hypoprussic or prussous acid. Since potash by vessel being kept warm, the oxide of iron will heat separates the hydrogen of the prussic acid, fall to the bottom; the clear part may be poured we see that in exposing a mixture of potash and off to be filtered through paper, taking care to animal matters to a high temperature, a true keep the funnel covered, so that crystals may prusside or cyanide of potash is obtained, for- not form in it by refrigeration. The residuum merly called the Prussian or phlogisticated al- may be treated with more water, and thrown kali. When prusside of potassium is dissolved upon the filter, upon which warm water ought in water, prussiate of potash is produced, which to be poured, until all the soluble part is washed is decomposed by the acids without generating away. By evaporation, and subsequent rest in ammonia or carbonic acid; but, when prusside a cool place, 145 grains of crystals of the prusof potash dissolves in water, no change takes side or cyanide of mercury will be procured in place; and neither ammonia, carbonic acid, nor quadrangular prisms. hydrocyanic vapor is given out, unless an acid "The following is a new process for obtaining be added. These are the characters which dis- the prussic acid :- Take of the prusside of mertinguish a metallic prusside or cyanide from the cury in fine powder one ounce, diffuse it in two cyanide of an oxide.

ounces of water, and to it, by slow degrees, add From the experiments of M. Magendie it ap- a solution of hydrosulphuret of barytes, made pears that the pure prussic acid is the most by decomposing sulphate of barytes with charviolent of all poisons. ' When a rod dipped into coal in the common way. Of the sulphuret of it is brought in contact with the tongue of an barytes take an ounce, boil it with six ounces of animal, death ensues before the rod can be with- water, and filter it as hot as possible. Add this drawn. If a bird be held a moment over the in small portions to the prusside of mercury, mouth of a phial containing this acid, it dies. agitating the whole very well, and allowing suffiA French professor of chemistry left by acci- cient time for the prusside to dissolve, while the dent, on a table, a flask containing alcohol im- decomposition is going on between it and the pregnated with prussic acid ; the servant, en- hydrosulphuret as it is added. Continue the ticed by the agreeable favor of the liquid, addition of the hydrosulphuret so long as a dark swallowed a small glass of it. In two minutes precipitate of sulphuret of mercury falls down, she dropt down dead, as if struck with apoplexy. and even allowing a small excess. Let the whole

Scharinger, a professor at Vienna,'' says be thrown upon a filter, and kept warm till the Orfila, prepared a pure and concentrated prus- fluid drops through; add more water to wash the

sulphuret of mercury, until eight ounces of Auid crucible, reduce it to powder, spread it on a have passed through the filter, and it has become muffle, and expose it to a white heat for half an tasteless. To this fluid, which contains the hour. Dissolve it in six times its weight of prussiate of barytes, with a small excess of hy- water, and filter the solution while warm. Pour drosulphuret of barytes, add sulphuric acid, di- this solution into a glass receiver, placed in a sand Cuted with an equal weight of water, and allowed furnace, heated to 170° or 180°, and then gradually to become cold, so long as sul-,' ate of barytes add the best Prussian blue in powder, injecting falls down. The excess of sulphureted hydro- new portions of it as the former becomes gray, gen will be removed by adding a sufficient por- and supplying water as fast as it evaporates; tion of carbonate of lead, and agitating very continue until the added portions are no longer well. The whole may now be put upon a filter, discolored ; then increase the heat to 212°, and which must be closely covered; the fluid which continue for half an hour. Filter the ley thus passes is the hydrocyanic or prussic acid, of obtained, and saturate it with sulphuric acid mowhat is called the medical standard strength.' derately diluted; a precipitate will appear :

Dr. Nimmo finds that prusside of mercury is when this ceases, filter off the whole, and wash capable of dissolving the mercurial peroxide. the precipitate. Evaporate the filtered liquor to Hence the above proportions must be strictly about one quarter, and set it by to crystallise : observed, if we wish to obtain this powerful after a few days, yellowish crystals of a cubic or medicine of uniform strength. Ile conceives, quadrangular form will be found mixed with therefore, that the ferroprussiate of potash should some sulphate of potass and oxide of iron; pick be taken for the basis of the calculation.

out the yellowish crystals, lay them on blotting Scheele found that prussic acid occasioned paper, and redissolve them in four times their precipitates with only the following three me- weight of cold water, to exclude the sulphate of tallic solutions; nitrates of siiver, and mercury, potass. Essay a few drops of this solution with and carbonate of silver. The first is white, the a solution of barytes, to see whether it contains second black, the third green, becoming blue. any sulphuric acid: filter off the solution from

The prussiates or hydrocyanates are all alka- the sulphat of barytes, which will have precipiline, even when a great excess of acid .is em- tated, and set it by to crystallise for a few days, ployed in their formation ; and they are decom- that the barytes, if any should remain, may be posed by the weakest acids.

precipitated. If the crystals now obtained be The hydrocyanate of ammonia crystallises in of a pale yellow color, and discover no bluish cubes, in small prisms crossing each other, or in streaks, wheu sprinkled over with muriatic acid, feathery crystals, like the leaves of a fern. Its they are fit for use, and should be kept in a well volatility is such that at the temperature of 711° stopped bottle, which, to preserve them from the it is capable of bearing a pressure of 17.72 air, should be filled with alcohol, as they are inches of mercury; and at 97° its elasticity is insoluble in it. equal to that of the atmosphere. Its great vola M. Gay Lussac prepared a hydrocyanate of tility prevented M. Gay Lussac from determin- potash and silver, which was quite neutral, and ing the proportion of its constituents. M. Gay which crystallised in hexagonal plates. The soLussac considers Prussian blue as a hydrated lution of these crystals precipitates salts of iron prusside of iron, or a cyanide having water in and copper, white. Muriate of ammonia does combination; and M. Vauquelin, in a memoir not render it turbid; but muriatic acid, by dislately read before the Academy of Sciences, re- engaging hydrocyanic acid, precipitates chloride gards Prussian blue as a simple hydrocyanate of of silver. Sulphureted hydrogen produces in it iron. He finds that water impregnated with an analogous change. This compound, says M. prussine can dissolve iron without changing it Gay Lussac, is evidently the triple prussiate of into Prussian blue, and without the disengage- potash and silver; and its formation ought to be ment of any hydrogen gas, while Prussian blue analogous to that of the other triple hydrocyanwas left in the undissolved portion. But prussic ates. . And as we cannot doubt, adds he, that acid converts iron or its oxidę into Prussian blue hydrocyanate of potash and silver is in reality, without the help either of alkalis or acids. lle from the mode of its formation, a compound of farther lays it down as a general rule, that those cyanide of silver and hydrocyanate of potash, I metals which, like iron, decompose water at the conceive that the hydrocyanate of potash and ordinary temperature of the atmosphere, form hy- iron is likewise a compound of neutral hydrodrocyanates ; and that those metals which do not cyanate of potash, and subcyanide of iron, which possess

this power, as silver and quicksilver, form I believe to be combined with hydrocyanic acid only cyanides.

in the white precipitate. We may obtain it perPrussic acid is easily separated from potash fectly neutral, and then does not decompose by carbonic acid, but, when oxide of iron is alum; but the hydrocyanate of potash, which is added to the compound, a triple salt is formed, always alkaline, produces in it a light and flocusually called ferroprussiate of potash. The me- culent precipitate of alumina. To the same exthod of preparing this salt practised by Klaproth cess of alkali we must ascribe the ochry color of is one of the best. It is as follows :-Prepare the precipitates which hydrocyanate of potash pure potass, by gradually projecting into a large forms with the persalts of iron. crucible, heated to whiteness, a mixture of equal M. Vauquelin has given the following very parts of purified nitre and crystals of tartar; elegant process for obtaining pure hydrocyanic when the whole is injected, let it be kept at a or prussic acid, from the cyanide or prusside of white heat for half an hour, to burn off the mercury :coal. Detach the alkali thus obtained from the Considering that mercury has a strong attrac

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tion for sulphur, and that prussine unites easily same reason which leads to the term cyanogen, to hydrogen, when presented in the proper state, would warrant us in calling it leucogen, erythrohe thought that sulphureted hydrogen might be gen, or chlorogen; for it produces, white, red, employed for decomposing dry cyanide (prusside) or green, with other metals, as it produces blue of mercury. He operated in the following way: with iron. -He made a current of sulphureted hydrogen By digesting red oxide of mercury with prusgas, disengaged slowly from a mixture of sul- sian blue and hot water, we obtain a prusside phuret of iron, and very dilute sulphuric perfectly neutral, which crystallises in long fourpass slowly through a glass tube slightly heated, sided prisms, truncated obliquely. By repeated filled with the mercurial prusside, and commu- solutions and crystallisations, we may free it from cating with a receiver, cooled by a mixture of a small portion of adhering iron. But M. Gav salt and snow.

Lussac prefers boiling it with red oxide of merAs soon as the sulphureted hydrogen came in cury, which completely precipitates the oxide of contact with the mercurial salt, this last substance iron, and he then saturates the excess of oxide blackened, and this effect gradually extended to of mercury with a little prussic acid, or a little the farthest extremity of the apparatus. During muriatic acid. The prusside thus formed is dethis time no trace of sulphureted hydrogen composed by heat to obtain the radical. For could be perceived at the mouth of a tube pro- common experiments we may dispense with ceeding from the receiver. As soon as the odor these precautions. of this gas began to be perceived, the process When this cyanide is boiled, with red oxide of was stopped ; and the tube was heated in order mercury, it dissolves a considerable quantity of to drive over the acid which might still remain the oxide, becomes alkaline, crystallises no longer in it. The apparatus being unluted, he found in prisms, but in small scales, and its solubility in the receiver a colorless fluid, which possessed in water appears a little increased. When evaall the known properties of prussic acid. It porated to dryness, it is very easily charred, amounted to nearly the fifth part of the prusside which obliges us to employ a water bath. This of mercury employed.

compound was observed by M. Proust. When This process is easier, and furnishes more decomposed by heat, it gives abundance of prusacid, than M. Gay Lussac's, by means of mu- sine, but mixed with carbonic acid gas. Proust riatic acid. He repeated it several times, and says that it yields ammonia, oil in considerable always successfully. It is necessary merely to take abundance, carbonic acid, azote, and oxide of care to stop the process before the odor of the sul- carbon. He employed a moist prusside. Had phureted hydrogen begins to be perceived, other it been dry, the discovery of prussine could wise the hydrocyanic acid will be mixed with it. hardly have escaped him. The prusside of merllowever, we may avoid this inconvenience by cury, when neutral and quite dry, gives nothing placing a little carbonate of lead at the extremity but prussine; when moist, it furnishes only carof the tube. As absolute hydrocyanic acid is bonic acid, ammonia, and a great deal of prussic required only for chemical researches, and as it acid vapor. When we employ the prusside made cannot be employed in medicine, it may be with excess of peroxide, the same products are worth while, says M. Vauquelin, to bring to the obtained, but in different proportions, along with Tecollection of apothecaries a process of M. azote, and a brown liquid, which Proust took for Proust, which has perhaps escaped their atten- an oil, though it is not one in reality. Hence, tion. It consists in passing a current of sul- to obtain pure prussine, we must employ the phureted hydrogen gas through a cold saturated neutral prusside in a state of perfect dryness. solution of prussiate of mercury in water, till The other mercurial compound is not, however, the liquid contains an excess of it; to put the simply a sub-prusside. "It is a compound of mixture into a bottle, in order to agitate it from oxide of mercury and the prusside. time to time; and finally, to filter it.

When the simple mercurial prusside is exIf this prussic acid, as almost always happens, posed to heat in a small glass retort, or tube, contains traces of sulphureted hydrogen, agitate shut at one extremity, it soon begins to blacken. it with a little carbonate of lead, and filter it It appears to melt like an animal matter, and agair.. By this process we may obtain hydro- then the prussine is disengaged in abundance. cyanic acid in a much greater degree of con- This gas is pure from the beginning of the procentration than is necessary for medicine. It cess to the end, provided always that the heat has the advantage over the dry prussic acid, of be not very high; for, if it were sufficiently inbeing capable of being preserved a long time, tense to melt the glass, a little azote would be always taking care to keep it as much as possible evolved. Mercury is volatilised with a consifrom the contact of air and heat. Dr. Nimmo's derable quantity of prusside, and there remains directions for preparing the prusside of mercury a charry matter of the color of soot, and as light ought to be attended to.

as lampblack. The prysside of silver gives out PRUSSINE, or Prussic Gas, in chemistry, likewise prussine when heated ; but the mercuthe cyanogen of M. Gay Lussac, is a peculiar rial prusside is preferable to every other. gas obtained by decomposing prusside of mer Prussine or cyanogen is a permanently elastic cury by heat. "The term cyanogen signifies the Auid. Its smell, which it is impossible to deproduce of blue; but as the production of blue scribe, is very strong and penetrating. Its soluis never the result of the direct action of this tion in water has a very sharp taste. The gas substance on any other single body, but an in- burns with a bluish flame mixed with purple. direct and unexplained operation of it in con- Its specific gravity, compared to that of air, is junction with iron, hydrogen, and oxygen, the 1.8064. M. Gay Lussac obtained it by weigh

ing at the same temperature, and under the same vescence, and the solution is strongly alkaline. pressure, a balloon of about two litres and a Its taste is the same as that of hydrocyanate or half (152-56 cubic inches), in which the vacuum simple prussiate of potash, of which it possesses was made to the same degree, and alternately all the properties. full of air and prussine. 100 cubic inches weigh The gas being very inflammable, M. Gay Lustherefore 55:1295 grains.

sac exploded it in Volta's eudiometer, with about Prussine is capable of sustaining a pretty high twice and a half its volume of oxygen. The deheat, without being decomposed. Water, with tonation is very strong; and the fame is bluish, which M. Gay Lussac agitated it for some mi- like that of sulphur burning in oxygen. nutes, at the temperature of 68°, absorbed about It is now obvious that the action of potassium four times and a half its volume. Pure alcohol on prussine agrees with its action on prussic acid. absorbs twenty-three times its volume. Sul- We have seen that it absorbs fifty parts of the phuric ether and oil of turpentine dissolve at first, and likewise that it absorbs 100 parts of least as much as water. Tincture of litmus is the second, from which it separates fifty parts reddened by prussine. On heating the solution of hydrogen. But 100 parts of prussic acid the gas is disengaged, mixed with a little car- vapor, minus fifty parts of hydrogen, amount bonic acid, and the blue color of the litmus is exactly to fifty parts prussine. Hence the two restored. The carbonic acid proceeds no doubt results agree perfectly, and the two compounds from the decomposition of a small quantity of obtained ought to be identical, which agrees preprussine and water. It deprives the red sulphate cisely with experiment. of manganese of its color, a property which The analysis of prussine being of great imprussic acid does not possess. This is a proof portance, M. Gay Lussac attempted it likewise that its elements have more mobility than those by other methods. Having put prusside of merof the acid. In the dry way it separates the cury into the bottom of a glass tube, he covered carbonic acid from the carbonates.

it with brown oxide of copper, and then raised Phosphorus, sulphur, and iodine, may be the heat to a dull red. On heating gradually sublimed by the heat of a spirit-lamp in prus. the part of the tube containing the prusside, the sine, without occasioning any change on it. Its prussine was gradually disengaged, and passed mixture with hydrogen was not altered by the through the oxide, which it reduced completely same temperature, or by passing electrical sparks to the metallic state. On washing the gaseous through it. Copper and gold do not combine products with aqueous potash, at different parts with it; but iron, when heated almost to white- of the process, he obtained only from 0.19 to ness, decomposes it in part. The metal is co 0:30 of azote, instead of 0.33, which ought to vered with a slight coating of charcoal, and be- have remained according to the preceding anacomes brittle.

The undecomposed portion of lysis. Presuming that some nitrous compound the gas is mixed with azote (contains free azote). had been formed, he repeated the experiment, In one trial the azote constituted 0.44 of the covering the oxide with a column of copper mixture, but in general it was less. Platinum, filings, which he kept at the same temperature which had been placed beside the iron, did not as the oxide. With this new arrangement, the undergo any alteration. Neither its surface, nor results were very singular; for the smallest that of the tube, was covered with charcoal like quantity of azote which he obtained during the the iron.

whole course of the experiment was 32-7 for 100 In the cold, potassium acts but slowly on of gas, and the greatest was 34:4. The mean of prussine, because a crust is forined on its sur- all the trials was,face, which presents an obstacle to the mutual Azote

33.6 or nearly 1 action. On applying the spirit-lamp, the potas Carbonic acid 66.4

2 sium becomes speedily incandescent; the absorp. A result which shows clearly that prussine contion of the gas begins, the inflamed disc gradually tains two volumes of the vapor of carbon, and diminishes, and when it disappears entirely, one volume of azote. which takes place in a few seconds, the absorp In another experiment, instead of passing the tion is likewise at an end. Supposing we employ prussine through the oxide of copper, he made a a quantity of potassium that would disengage mixture of one part of the prusside of mercury, fifty parts of hydrogen from water, we find that and ten parts of the red oxide, and after introfrom forty-eight to fifty parts of gas have disap- ducing it into a glass tube, close at one end, he peared. On treating the residue with potash, covered it with copper filings, which he raised there usually remains four or five parts of hy- first to a red heat. * 'On heating the mixture sucdrogen, sometimes ten or twelve. M. Gay cessively, the decomposition went on with the Lussac made a great number of experiments to greatest facility. The proportions of the gaseous discover the origin of this gas. He thinks that mixture were less regular than in the preceding it is derived from the water which the prusside experiment. Their mean was,of mercury contains when it has not been suf

Azote

34:6 instead of 33.3 ficiently dried. Prussic acid vapor is then pro Carbonic acid

65.4

66.6 duced, which, when decomposed by the potas. In another experiment he obtained, sium, leaves half its volume of hydrogen. Potassium, therefore, absorbs a volume of pure

Azote

32.2 prussine, equal to that of the hydrogen which it

Carbonic acid

67-8 would disengage from water.

Now the mean of these results gives The compound of prussine and potassium is

Azote

33:4 yellowish. It dissolves in water without effer

Carbonic acid

66 6

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