CLIII. 011 some Chemical +$?cts produced by Platillurn. B-y fir. C. F. L CCHCENBEIN. SOME time ago I published an account of’a series of expe-riments made with the resin c)fgu:tiacurn from which it appeared that the substance named is inst:intly reridered blue not only hy chlorine and nitrous acid but also by bromine iodine ozo~ie,aiid it tiiirnber of metallic peroxides. Free oxygen lie it pure or mixed with nitrogen hydro- gen iiiid carbonic acid gas does not act in the dai*k upoii that ~*esi~ious matter and comparatively very little wheri exposed to the action of solar light. From these thcts it beconies mani- fest that 0xyg.m must have assumed a peculiar condition of cheniical excitement before it is capable of‘ causing the re-action mentioned.The beautiful experiments both of Ihvy and Doebereiner have demonstrated that platinum has the power to occasioii the oxidation of‘ a nuniber of suljstiinces under circumbtances in which that chemical action would riot take place wittiout the agency of that metal. ‘1’1~ blue coloration which the resiii of guaiacuni assumes under certain circumstances is most likely dependent iipori ;I partial oxidation of‘ that substance niid the latter being 50 very sen-sible to oxygeri that happens to be chemically excited it could easily be conjectured that platinum in a state of niinute mechanical divisioii put in contact with the resinous sul)staiice ineritioned niigtit cause the oxidation of the latter in the same manner :is that nietal occasions the oxiciatiori of‘ hy drogen aetlier and alcoliol.l’he fitcts I mi going to state will show that the correctness of this corijecture is fully borne out by experiment. Kewly-prepared spongy platinuni being placed lipon a piece of filtei-ing paper that had previously been rlrenclied with an alcoholic solution of resin of guaiaciim caused rather rapidly the appearance of blue spots at the place where the nietai had been in coritact with the resiiious solution. My experiments Chcm. SOC.Meni. VOL. I~J. C Dr. Schoenkin oia some Chemical Efects have further shown that that reaction takes place the more ra-pidly and intensely the more divided the platinum happens to be of which we make use in the experiment described. What is called Platinum Black acts therefore more energetically than spongy platinum does.From the facts stated it appears that platinum in a state of minute mechanical division con-ducts itself towards resin of guaiacuin like the simple halo- genous bodies ozone and a number of metallic peroxides. These facts demonstrate also that the coloration of the resin- ous matter being caused by platinum belongs to that series ofph~nomenawhich takes place when that metal is put in contact with a mixture of’oxygen and hydrogen oxygen and vapour of zether &c. In the paper above alluded to I have pointed out the re- markable coincidence that all the substances having the power of rendering blue the resin of guaiacum possess also the property of deconiyosing iodide of’ potassium transforming the yellow prwsiate of potash into the red one and I add decomposing sulphure tted and iod wetted hydrogen trans-forming sulphurous acid into sulphuric acid and destroying organic colouring matters.We shall presently see that pla- tiiium ill a state of miiiute mechaiiical division has the same power. If a crystal of pure iodide of potassinm be put upon a piece of filtering paper that has previously been moistened with di-stilled writer antl sporigy platiniini be placed upon that paper the spot touched by the metal assumes rather rapidly a brown- ish red colour. Tl’liis coloration does not result from free iodine but is most likely due to a compomd consisting of periodide of platinum antl iodide of potassium. That conjecture is founded upon the following facts.If a solution or iodide of potassium is put in contact with spongy platinum or platinum black the former assumes a perceptibly red colour which dis- appears on heating the solution to its boiling-point. Now it is well known that the cornpound before mentioned yields with water a red solution the colour of which is destroyed by heat Neither the red solution nor the brownish-red spots before mentioned are able to render blue paste of starch another proof that there is no free iodine in the case. The reaction described is most likely brought about in the following nian- ner the chemically excited oxygen surrounding the spongy platinum decomposes iodide of potassium a peculiar peroxide of potassium being formed and iodine eliminated.The latter in its nascent state combines with platinum to produce the periodide of that metal which itself unites with iodide of po-tassium into that compound yielding with water a red solw- p,,oduced by Plalimnt. tion. It is worthy of remark that a solution of iodide of potassium having been treated with spongy platinum enjoys the property of colouring blue the paste of starch on being mixed with dilute and pure sulphuric acid. The same re- action is exhibited by the same solution after it has been treated either with ozone or peroxide of lead. If some drops of a weak i. e. colourless solution of the yellow prussiate of potash be added to platinum black that solution assumes a perceptibly yellow colour arid yields with a solution of' che-mically pure sulphate of protoxide of iron a blue precipitate.From these facts it seems to follow that platinuni has the power to transform the yellow prussiate into the red one. Some years ago I tried to show that spotigy platinum being placed in an atmosphere of sulphuretted hydrogen loses its property of acting upon detonating gas on account of a film of sulphur being deposited on the surface of the metal. Such beiiig the case it would follow that spongy platinum has the pro erty to decompose sulphuretted hycirog:en. 8ulourless hydriodic acid on being mixed up with some platinum black assumes a brownish yellow coloui. which re- action indicates an eliinination of iodine. Several chemists particularly Dcebereiner Phillips arid Urunner have ascertained that spongy platinum produces sul-phuric acid on being placed in contact with moist oxygen anti sulphurous acid and there is no doubt that platinum black put into sulphurous acid gives rise to the fbrmation of sul-phuric acid.Moist filtering-paper being coloured by a soiu-tion of indigo and put in contact with spongy p1:itirium for about twentyfour hours appears entirely bleached at those spots which had touched ttie metal. I have repeated this ex- periment more than thirty times and always with the snnie result. This remarkable fact proves that platinuni in a state of minute mechariical division has the power of destroy-ing organic colouring matters and acts as a real tdeachiilg agent. Before passing to other subjects I must tiot omit to mention a circumstance which seems to me meriting some attention.It is a curious fact which has not escaped ttie notice of chemists that in more than one case platinum acts exactly like common eledcity both of them determining at the conimon temperature for instance the oxidation of free hydrogen. Now it being well known that nitric acid is formed if' electrical sparks are made to pass through moist air it seemed to me within the reach of possibility that the same acid might be prodwed by platinuni if that metal in a state of minute mechanical division were placed in contact with moist atmospheric air. Witli the view of ascertainiirg the c2 111,.Sichwiibein on sme Chmzicnl l$Gcfs correctness of that conjecture I put a piece of moist litmus p:iper in close contact either with spongy platinum or with platilium black.111 some cases part of the paper exhibited ;i slight reddish coloration part of‘it proved to be entirely bleached or iiearly so. I must however not omit to state that in the great miijority of my experinien ts I obtained bleach- iiig effects only aiitl no reddening of the litmus paper what-ever. I am u~ialile to account filr the difference of the results meritioiierl. Was the reddening of the litmus paper caused by some traces of nitric acid formed under the circumstances iiidicated ? 1am iiot prepfired at all to aiiswer that question. If nitric acid shoiiltl however Ipppeii to be produced under the circumsttinces irientioneci it would be a fkt in my opinion not very difficult to be :~ccouiited for.In whatever state the oxygen surrouiidiiig platiiiuni n121y be certain it is that that state is such as to i*ender oxygen very apt to combine at the common teniperature with a number of oxidable substances that would not be oxidized by common oxygen without the presence of pl;itiniini. ‘lY~etormation of nitric acid taking place under the circuiristaiices mentioned would indeed be a fact very similar to the comt,ustion OF detonating gas caused by platinum. 1 repeat however ttiat I consider the geuera- tion of nitric acid bi*oLigtit ahout by the agency of platinum as fiir from being est:tblistie~l by decisive facts. The voltaic chni-acter of bodies being so intimately con-nected with their chetnical riatiire that in most if not in all cases we may irif’er the one frum the other the fact I am going to state merits our attention.Clilorine bromine iodine ozone aiid a number of nietallic peroxides enjoy consider- able electro-niotive powers which are of such a kind as to render those bodies what is commonly called electro-negative. Ehce it conies that :t piece of metal being covered with any one of the bodies naiiietl bears to another commoii piece of the same metal the same voltaic relation as copper does to zinc. According to the experinierits of De In Rive and some other philosophers platinum foil being covered with some spongy .platiiium is negative to conimon platinum plate a lact which proves that in a voltaic point of view there exists a great analogy between the simple halogenous bodies ozone and metallic peroxides on one side and spongy platinum on the other.After hving stated n number of facts which clemonstriite the highly oxiclizirig powers of platinum we ask in what manner does that metal exalt the chemical activity of oxygen? Ttlis question has occiipiecl marly philosophers arid been answered in ve1.y different ways. Faratlay and Doebereher. p*o(Judby Hcriiir tun. ascribe to platinum the power of condensing oxygen so much as to deprive that element of its gaseous condition and think that coiidensed state to be the true cause of the oxidizing powers of platinum. Others (De la Riveand Gmelin) presume that oxygen is capaljle of cheitiically uniting with that metal and with those philosophers it is the oxide of platiniini that occasions the oxidation of Iiydrogen &c.Berzelius holds the opinion that the oxidatiotis caused by phtiiiuin are catn- lytical pht.mornena i. E. effects produced by some unknown force being innate to that nietal and ex;ilting the chemical attractive powers of oxygen. It is not my inteiition to enter into a discussion of those opinions; I shall confine myself to :I fkw general remarks tipon that interesting subject. As the conimon oxides of pla-tinum are not acted upon (at the common temperature) by free hydrogen as platiiium foil or wire that causes at a mode-rate temperature the combustion of (letonating gas exhibits :I perfect metallic surfkce while tlie tliirinest film of’ an oxide diniinishes or destroys the lustre of any metal and as pla-tinurn is a body that has a very weak affinity for oxygen I think that that nietal is nut capable of combining directly with the oxygen of’the air an(1 that De la Rive’s view of the subject is erroneous.Rut how is it with Fsraday’s and Doe-bereiner’s theory of the matter in question? It seems indeed to be tlie true one. Satisfactory however as that hypothesis may appear it is nevertheless possible that the oxidizing ac; tion of‘platinum may depend upon a cause different from what the philosophers tnentioned- consider as such. We know that phosphorus being put in contact with nioist atmospheric air gives rise to the formation of H highly oxi- dizing agent which as it has been shown elsewhere seems to be a peculiar compound of water and oxygen and enjoys the power of oxidizing a great number of substances at the comni~iitemperatiire.Now if phosphorii~enjoys that pro- perty it seems possible that some other substances for in-stance platinurn and iriditim niay do the same. In other ternis it appears possible that platinrim has the power to en- gender out of free oxygen and water a highly oxidizing per- oxide which surrounding that metal empowers the latter to cause all the oxidations ahove nientioned. In comparing the clieniical properties of platinum when minutely divided with those ofozone we cannot help being strnck by their great simi- larity as will appear fkom the following statements :-1. Both substances possess a negative electro-motive power.2. Both of theni destroy organic colouring matters. 3. Both of them reiider the resin of guaiacum blue. Ih. Schanbein 01) some Chemical Eects 4. Both of them decompose iodide of potassium. 5. Both of them change the yellow prussiate of potash into the red one. 6. Both of‘them transform sulphurous acid into sulphurie acid. 7. Both of them decompose oxalic and formic acids. 8. Both ofthein act in a sirniltir way upon Ether and alcohol. Great as the simihrity of properties may be it does not fol- low that platinum owes its oxidizing powers to a film of per- oxide of hydrogen being foriwct round the metal by a cata-lytical action of the latter.I have not yet succeeded in prod ducing by the means of spongy platinum and moist air an atmosphere exhibiting the peculiar electrical smell bleach- ing power and oxidizing properties which belong to ozone. Considering the great volatility of the last-named substance we shoiild slippose that it ought to disperse into the sur-rounding medium as soon as formed; or should ozone he re-tained by platinum in a way similar to that in which we think oxygen is attached to and condensed around that metal? Sup-posing oxygen to be an odoriferous substance it is manifest that the oxygen actually condensed by platinum could not affect the olt‘actory rierves. Another objection might be raised to the conjecture that it is a film of‘peroxide of’hydrop to which platinum owes its clxidizing powers from the fact that Thenmd’s oxygenized 11ater is really decomposed I)y platinum.Considering how- ever that ozone is in some respects strikingly different from Tti enn1. tl’s conipoun d,11av i11g for i nstaxice a pecu1iar odour being insoluble in water transforming both metallic silver and it.; basic oxide into a peroxide it appears possible that uzone is capa\)le of existing in the clcsest contact with pla-tinum without suffering deconiposition. I am not aware of sporigp pIatinuni or platinum black having been treated with ;inhydrous oxygen and I do riot know whether it has been ascertained if the latter is absorbed as easily by that metal :IS moist oxygen. It is equally unknown to me whether platinum after being placed in dry oxygen or air exhibits t!ie same properties as platinum after beiiig exposed for some time to the same gases when moist.If the oxidizing powers of platiuum should depend upon a film of peroxide of hydro-gen attached to that metal it is obvious that spoiig pltt-tinun; freed from its adhering water and placed withiii com-pletely dry oxygen could not assume oxidizing properties. Supposing however that spongy platinum acquires oxidiziiig powers under the circumstances mentioned we rimy never-theless imngiiie that those powers depend iipoii a filni of per pr.odnctd hy P~otit1t4/11 oxide of hydrogen surrounding that metal. De la Rive’s nnd Marignac’s experiments have shown that oxygen obtained from fused chlorate of potash on being exposed to the action of electrical sparks yields perceptible quantities of ozone.Now taking that odoriferous substance for a peroxide of hy-drogen we must admit that even that oxygen which is consi-dered as absolutely anhydrous still contains traces of aqueous vapour. ‘Taking for granted the hiiniidity of what is called dry oxygen we may easily conceive how platinum brought into an anhydrous mixture of oxygen and hydrogen could cause the comtiustion of the latter. Oiit of some oxygen and the traces of water still contained in what is considered anhy- drous detonating gas a film of peroxide of hydrogen would be formed around the spongy platinum ; that peroxide in the very moment of its being erigentlerd would oxidize n neigli-bouring portion of’ free hydrogen.The heat resulting fiiorn that oxidation would determine another portion of hydrogen to unite with oxygen. The heat proceeding from that che- mical union would occasion the combustion of an additional portioti of hydrogen and so on until the whole of the detona- ting gas should be consumed. The minute quantity of the peroxide of hydrogen attached to the spongy platinum woulcl act like a small conimon or electrical spark which as we we11 know is capable of setting the largest volume of detonating gas on fire. Electrical sparks acting upon a mixture of oxy- gen and hydrogen exactly in the snnie WRY as spongy pla- tinum does and it being a well-ascertained fact that ozoiie makes its appearance on causing common electricity to pass through (moist) oxygen it is possible that electricity and pln-tinuiii occasion the oxidation of hydrogen because both of them are able to produce ozone anti that it is to the agency of that odoriferous substance that we are to ascribe the che-mical effect mentioned.That conjecture must 1,ecome still more plausible if we take into account the Lict that spongy plntioum acts in a variety of other cases exactly like ozone. Taking this view of the case we could not admit that an electrical spark has the power to cause directly the formation of‘water out of detonating gas but should be obliged to con- sider the oxidation as occasioned by the ozone being formed under electrical influence out of aqueous vapour and oxygen In other terms we are obligeti to ascribe the oxidation to the same cause from which we derive the decomposition of iodide of potassium the transformation of the yellow prus- siate of potash into the red one the destruction of vegetable colouring matters the turning blue of the resin of guaiacunt the transformation of the protoside of lead into the peroxide Mr.J. E. Teschemacher on the &c. brought ahit by the electrical brush. Now as it can hardly be doubted any longer that the chemical eff'ects just stated are due to ozone produced by electricity the conjec- ture according to which free hydrogen may also he oxidized by electrical ozone seems to be very probable. Jntleed if po-tassiuni the hydrogen of colouring matters the oxide of lead &c. are oxidized by the oxygen of electrical ozone why should free hydrogen make an exception to the rule? But however that riiay be the subject under discussion seems to be iuterestiilg ai-rcl I add still obscure enough to offer an induceiiieut to chemists to apply themselves to its elucidutioii by further investigatioiis.The matter merits our atteiition the niore that it bears so close a relation to that series of chemical phamornenn which are called catalytical actions and which certaiiily belong to the most enigmatical facts ot' our science.