Prof. Bunsen on Cucodyl Compounds containing Platinum. 63 X. On a new Class of Cncodyl Compounds containing Pla-tinum. BY ProJessor BUNSEN ofMarBurg*. Read December 7 1841. a former paper I have endeavoured to prove from the IN,umerous instances of substitution presented by nlcarsin that this substance contains a ternary radical composed of arsenic united to a carbo-hydrogen (C H + As,) and en- tering into composition with elementary bodies like a metal in a manner not hitherto observed. This opinion has been confirmed by niy subsequent experiments and may be consi- dered of considerable importance in the question of compound radicals. The chloride of this radical is reduced by those metals which decompose water at a temperature not exceed- ing that of boiling water; the free radical separating in the form of a clear aethereal fluid which oxidates in the air with more rapidity than potassium and produces two degrees of oxidation by it5 combustion namely an acid and an oxide both of which can be again reduced by deoxidizing agents.The analogy between cacodyl and the metals extends still further ; for that radical unites directly with the non-metallic elements forming substances of the same nature as are pro- duced when hydracids combine with the elements of metallic oxides water being produced. It will be seen from what has been said that this substance bears a greater resemblance than most other compound bodies to ammonia. Vnder this impression I tried the action of clzloride of platinum on it and have been fortunate in ob- taining a class of conipounds analogous in composition to those of Gros and Reiset ; supposing the ammonia in the latter replaced b_v cacodyl.The results obtained tend to throw a new light on the relations in which the organic bases or alka- loids stand towards the simple oxides of metals. Translated from the German MS.of the author by Dr. T.G. Tilley. 64 Prof. Bunsen on Cacodyl Compounds containing Platinum. Chloride of Cacoplatyl. By mixing an alcoholic solution of chloride of platinum with a similar solution of chloride of cacodyl a precipitate of a reddish-brown colour is obtained which when washed with alcohol and rediiced to powder becomes yellowish-red and is inodorous. When this powder is heated it melts into a clear yellow gummy mass gives off hydrochloric acid and vapours smelling of chloride of cacodyl and leaves behind a gray-co-loured arseniuret of platinum.Both the chlorides of‘ pla-tinum and cacodyl are indicated in this conipound by reagents. ShouCd this compound be analogous to the chloride of caco-dgl its composition would be Pt C1 + Kd C1. This body, however could not be analysed for it is so easily decomposed as not to be of uniform composition. If the precipitate in question be boiled with water a yellowish solution is formed alcargen being generated at the same time and the solution on cooling deposits white needle-shaped crystals. This sub- stance may be named chloride of cacuplatyl and fiom this name the others will be derived.To obtain the chloride of cacoplatyl in larger quantities and in a more easy manner an aqueous solution of chloride of platinum is boiled with chlo- ride of cacodyl. The precipitate which falls first of a brown colour is changed by boiling into a wine-yellow colour. The precipitation of the chloride of cacoplatyl commences even during the boiling and by cooling still more is deposited. The mother liquid contains nothing except a little alcargen (or perhaps a true salt of cacodylic acid and oxide of platinum). The crystals are collected on a filter and purified by redis- solving. This compound possesses the following properties :-it crystallizes from a hot solution in long sharp needles which are beautifully formed is inodorous its taste disgustingly arsenious.It is soluble in hot alcohol and water more sparingly so in these liquids cold. When heated it becomes yellow then brown and without melting takes fire and burns like tinder,. giving off vapours smelling of arsenic and leaving behind fusible arseniuret of platinum. Sulphuric acid by depriving the compound of water turns it yellow. Hydro-chloric acid has no action. In amriionia it is soluble in all proportions ; by evaporating the solution imperf’ect crystals are formed which are insoluble in alcohol. Iodide of potas-sium produces in the solutions of chloride of cacoplatyl a yellow precipitate which dissolves of a reddish-brown colour in ammonia. With bromide of potassium a compound cry- stallizing in long silky needles is formed.Cyanide of potas- sium gives a yellowish white precipitate. By nitrate of silver Prof. Bunsen on Cacodyl Compounds containing Platinum. 65 the chloride of silver is thrown down without destroying the neutrality of the solution. The elementary analysis of the chloride of cacoplatyl dried at 110' C. was made by means of oxide of copper in a com- bustion tube the free space left in the tube being filled with tarnings of copper". In a second analysis chromate of lead was used; the results were the same:- 1. 2. Substance . . . . . 1.440 1-0194 Carbonic acid . . 0.494 0.3480 \Vater. . . . . . . 0956 0'2475 The chlorine was estimated by heating the compound to red-ness with caustic lime. 1.0873 gramme of substance gave 0.580 chloride of silver or 0-0225 silver ; by direct precipi- tation from the solution by nitrate of silver from 0.987 of sub-stance only 0'353 chloride of silver or 0'1405 silver was ob-tained.The estimation of the platinum and arsenic is attended with some difficulty from the circumstance that chloride of cacoplatyl is not perfectly. oxidized by nitric acid. 0.850 gramnie was therefore heated in a combustion tube with a mixture of 1 part of carbonate of soda and 3 parts of chlorate of potash. The contents of the tube after digestion with water left r2 quantity of arseniuret of platinum. The solu- tion which was coloured yellow by a little of the double chlo- ride of platinum and potassium was thrown on a filter and the arsenic containing platinum again collected.This last was dissolved in aqua regia and some silicic acid derived froni the combustion tube separated. The fluid freed from silicic acid and evaporated to dryness was again dissolved in weak alcohol and gave 0*752 gramme chloride of platinum and potassium. Besides this 0*018 platinum was obtained by heating a quantity ofsulphuret formed by transmitting through the solution a stream of sulphuretted hydrogen. The fluid when filtered was made use of for obtaining the quantity of arsenic; it was freed from alcohol by boiling deoxidized by sulphurous acid and precipitated by sulphuretted hydrogen. It gave 0.458 of sulphuret of arsenic from which by oxidation with nitric acid 1*254 of sulphate of barytes was obtained. These analyses conduct to the following formula for chlo- ride of cacoplaty1:- * This precaution is necessary lest some chloride of copper be carried into the chloride of calcium tube with the watery vapour ; when metallic copper is present a basic chloride of copper is formed which is not volatile.66 Prof. Bunsen on cacodyl Compounds contaz'nz'ig Platinum. 1. 2. Carbon c . . Hydrogen H . . Arsenic As . 305'7 87-4 940-0 9'44 2.70 9*49 2.75 29-54 9-52 2.73 29.29 Platinum Pt . . 1233.3 37'98 38.34 Chlorine CI . . 442.6 13.48 13-85 13.79 Oxygen 0,. . 200.0 6.39 6-32 3209.0 1oo*oo 100'00 The agreement between the carbon hydrogen and chlorine found and the numbers obtained by calculation proves with- out doubt that the following empirical formula C H As Pt CI 0,,is correct.It appears certain that this compound con- tains an atom of water not as water of crystallization but in another form for the compound may be heated to 164O C. without decomposition. At that temperature the colour is changed to a citron yellow and an atom of water is 'given off; which however is reacquired when the substance is boiled with water. 0'9767 loses by 210' C. 0'037 and no more although the temperature is raised to 240' C. The compound con- tains therefore 3-79 per cent. of water which corresponds to 1 atom and can be replaced by Z atom of ammonia. Bromide of Cacoplu{yl. This compound is formed when a hot solution of the chlo- ride of cacoplatyl is mixed with bromide of potassium; the crystals obtained are redissolved and recrystallized twice.They possess great similarity to the chlorine combination and form small yellow needles by the quick cooling of the aqueous solution; but when the solution is allowed to cool gradually the crystals formed are large well-shaped and co- lourless. They are pretty soluble in hot but only sparingly soluble in cold water. They have a feeble acid reaction are inodorous but possess a decidedly disagreeable arsenical taste which is bitter and astringent and remains long on the palate suggesting alcarsin. At 120O C. they lose their water and become yellow. At 240' C. this compound begins to be decomposed becoming gray at that temperature ; and when the heat is increased to 246" C. it melts into a black fmtid mass.At a higher temperature it takes fire in the air and burns like tinder leaving the arseniuret of platinum in shining scales. The analysis of this compound is equally simple with that of the preceding chlorine compound and is made by combustion with oxide of copper; the anterior part of the tube being filled with copper turnings. Prof. Bunsen on Cacodyl Compounds contninhg Platinum. 67 Dried at 1003C. 1. 2. Substance . . . 0'8895 1.1347 Carbonic acid . . 0933 0'34'73 Water . . . . * . 0.190 0*0249 To estimate the quantity of the bromine 0-7145 gramme was dissolved in water precipitated by nitrate of silver and boiled some timewith nitric acid by which 0.452 bromide ofsil- ver wasobtained. This research gives the following numbers:- Carbon c4.. 305-76 Calculated. 1. 2. 8-17 8.16 8'37 Hydrogen H . . 87-36 2.33 2*39 2.41 Arsenic As . 940-08 25-10 Platinum Pt .L. 1233026 32-93 Bromine Br . . 978-30 26-15 26.56 Oxygen 0,.. 200gO0 52.34 3744-76 100*00 To determine the proportion of water in the substance 1.2534 gramme was dried at looo C. and then heated in an oil-bath at Zooo till no more weight was lost. The loss was 0°040 which is equal to 3*200per cent. It will be seen that this compound like that of chlorine contains 1 atom of water. The formula for the hydrous and anhydrous compounds respectively are Pt 0 C €3 As Br Pt 0 C H As Br. In this compound also the water can be replaced by ammonia. ?odide of Cacoplatyl. The yellow precipitate which iodide of potassium forms with chloride cf cacoplatyl is this iodide.By mixing the two solutions boiling hot and tolerably dilute the iodide separates in the form of glistening scales of a silky lustre resetnbling the iodide of lead. It possesses nearly the same degree of solubility in water as the last-named substance. The iodide differs from the other compounds of cacoplatyl in losing its whole water at 100' C.; it becomes then of a brown violet colour without melting. The brown crystals dis- solve in water forming a yellow solution which deposits cry- stals again on cooling. This compound also is inodorous and may be submitted to ;Ihigh temperature without decomposition. It is in.jured at 260' C. when the compound melts and becomes black giving off dark vapours smelling like alcarsin and lastly burns like tinder leaving the arseniuret of platinum.For the analysis of this substance it was dried and burned with oxide 68 Prof. Bunsen on Cacodyt Compounds containing Platinum of copper and copper-turnings which last prevent any error arising from iodine passing over. 1. 2. Substance. . . 1.4322 1'1 46 Carbonic acid 0*3745 0.300 water . . . . 0*2510 0*400. To estimate the iodine 0*6685of the salt dried at 100' C. was precipitated from solution by nitrate of silver the preci- pitate being afterwards boiled in nitric acid. This trial gave Cal c 11t ated. I. 2. Carbon C .. 305.76 7.22 7-23 7'24 Hydrogen €3,. . 74'88 1-77 1.95 94 Arsenic As . 940'08 22-22 Ylatinum Pt.. 1233.26 29.14 Iodine I . . 1578*28 37-29 96-58 Oxygen 0 . . 100*00 2.36 4232.62 lOO*OO Sulphate oftgze Oxide of Cacoplatyl. To prepare this compouiicl a solution of 20 parts of the chlo- ride of cacoplatpl dried at 100' C. is boiled with 12-17 parts of dried sulphate of silver till the solution is not rendered tur- bid by salts ofsilver or chlorine. The filtered fluid is evapo-rated in vacuo over sulphuric acid till crystallization begins. At this degree of concentration it trace of the chloride of' sil-ver which bad remained dissolved is precipitated. The chlo- ride of silver is separated by filtration and the solution again evaporated in vacuo and over sulphuric acid till the greater part of the salt is deposited. The salt is purified by pressing it between folds of'bibulous paper.Thus prepared it has the form of white hard crystalline grains which appear under the microscope to be prismatic. This salt is inodorous but possesses a bitter and astringent taste which after a time sug-gests a relation to the cacodyl compounds. It does not deli- quesce nor is it decomposed by contact with air. It may be heated to 160° C. without injury; a few degrees higher its colour becomes gray then black giving off vapours smelling of cacodyl and lastly it takes fire and burns like amadou leaving behind an arsenical compound containing platinum which is fusible. To ascertain the quantity of water contained in this com-pound 1*078gramme was dried for 24 hours over suiphuric acid and then again for six hours at a temperature of looo C.the loss of weight was O-GO45 gramme. By heating it for three hours longer at 140' C. it lost 0°0025gramme. It thus appears that this conipound parts with its hygroscopic water Prof. Bunsen on Cacodyl Compounds containing Platinum. 69 with difficulty. It contains no more water which can be driven offby any elevation of temperature. 1.0390 gramme of this salt dried at 140° C. burnt with chromate of lead gave 0.2395 water and 0'340 carbonic acid. 0.5491 gave 0*1290water and 0'175 carbonic acid. 1-0474 gramme dissolved and precipitated by nitrate of ba-rytes gave 0-047'46 sulphate of barytes. These determinations give the following composition :-1. 2. 9-08 Carbon c4 . . 305'7 Calculated.8.81 8'81 Hydrogen H . . 87-4 2*6G 2.56 2.61 Arsenic As . . 940.0 27.91 Platin urn Pt . . 1233.3 36-62 Oxygen 0 . . 300'0 8-91 Sulphuric acid S 0 . 501.2 14.88 15.57 The characters of the chloride of cacoplatyl are so well marked and its relations to other bodies so manifest that we cannot be in doubt for n moment as to its rational composition. One glance at its empirical formula will satisfy 11s that here as in the compounds of cacodyl the most electro-negative element chlorine can by analogy be replaced by bromine and iodine just as oxygen is replaced by sulphur. The man- ner in which this substitution takes place is not different from that which we observe in the inorganic saline compounds. The chloride of cacoplatyl treated with the iodide of potas-sium gives up its chlorine to the potassium while the iodine goes over to the other element of the formula from which the potassium Has withdrawn the chlorine.The order of affinity of chlorine iodine and bromine for the substance in question bears a perfect analogy to what we observe in the inorganic haloid salts. The iodine is here set free by chlorine and bro- mine as in these salts while bromine is removed by chlorine only. Such an agreement in relation shows a similarity in the form of the groups of the elements and indicates that here as in the inorganic haloid compounds there are two divisions in the formula one of which represents the metal the other the halogenous body or salt-radical. We can express it thus:-Pt 0 C H As + C1.The first division of this formula which I have called caco- platy] represknts a peculiar and remarkable radical forming classes of compounds possessing great interest and giving an insight into the relation in which the vegeto-alkalies stand with regard to organic radicals. As the vegeto-alkalies when heated give off ammonia so our compound gives off water and this water can be replaced by oxides of metals. If we 70 Prof. Bunsen on Cacodyl Compounds contai?zi?g Plrrtinzrm. remove this atom of water in the formula we have remaining one atom of oxide of platinum and one atom of cacodyl which will explain the forination of these compounds in the simplest manner. The rational expressions may be thus given :-For the anhydrous chlorine compound Pt 0 Ka +Cl For the hydrous ...H 0 PtOKa+ C1 For that containing ammonia .....N H Yt 0 Ka +C1 For,the oxide .............H 0 Pt 0 Ka +0 For the sulphate .......... (HOPtOKa+O) SO The nature of this composition proves that the power of inorganic acids to unite with certain organic bodies without losing their power of saturation is not alone possessed by acids but that bases have also the same property; for in the present case the oxide of platinum bears a relation to the oxide of cacodyl similar to that which sulphuric acid does to benzoic acid in sulpho-benzoic acid. In the latter the ben- zoic acid is as little indicated by reagents as the oxide of pla-tinum in the cacoplatyl; and as the double acid referred to neutralizes only one atom of base so the double base in question saturates only one atom of acid or that quantity which the quantity of oxygen in the oxide of platinum indi- cates.A comparison of this new class of compounds with that discovered by Gros and Reiset will afford another reason for admitting the constitution which has been assigned to them. Reiset has rendered certain the existence of a body composed of the elements of 1 atom water 2 atoms atnmonia and 1 atom oxide of platinum which does not lose its atom of water when it enters into combination with oxygen acids and contains precisely as cacoplatyl 2atoms of oxygen and saturates 1 atom of acid. Berzelius affirms that these salts contain the oxide of ammonium. Here ammonia is combined with the oxide of platinum as the naphthaline is in sulpho-naphtbalic acid viz.(Pt 0N H, N H,+ 0)S0,. The simple relation in which this salt stands to the caco- platy1 compound must therefore not be passed over. The latter is nothing else than such a salt in which the ammo- nium is replaced by cacodyl. Its relation to ammoniuni in the electrical series of compound radicals is like that of an electro-negativ.e metal to an electro-positive he as for in- stance iron to potassium. It cannot however be denied that while the compound of Reiset is a strong caustic base the oxide of cacoplatyl forms only salts of an acid reaction. The analogy which the vegeto-alkalies and their composith show is so great that it permits no doubt as to the identity of their Mr.E. Schunck on Lecanorin &. constitution with that of this body. It now only remains for me to show by comparison the greatness of this analogy by the.. substitution of the platinum compound by an organic oxide. Reiset's Compounds. N H3,Pt 0,N H4 + C1 H Pt Kd + GI ((320 H,) 02 N H + GI N H,,Pt 0,N H4 + I H$tKd+I (C20 H,) 02 N H4 + 1 NHa,PtO,NH,+ 0 . Hl%Kd+O ((320 H,) 02 N H4 + 0 (N Hj Pt0,N H4 + 0)S 0,. (HPt Kd + 0)S 03. (C20H,02N H + 0)S 0,. The formation of urea (a body which possesses all the pro- perties of an organic base and may be considered as a cyanate of oxide of ammonium) belongs to the same class of pli~no-mena. In that compound an oxide of cyanogen (cyanic acid) occupies the place of the oxide of platinum in Reiset's ammo- nium COIII~OU~~, and unites with ammonium to give rise to a compound radical if such it may be considered.The radical (-Cy0 N H4)which forms part ofurea is in every relation similar to cacoplatyl; the oxide of that radical or urea being of all this class of compounds that which approaches most closely to the oxide of cacoplatyl (Cy 0,N H4)+ 0=urea.