1104 BRUSTBAIJ) THEl HYRROLYSIS OF CXXV.-The Hydrolysis of Platinum Salts Part I. Pot assiuni PI u tinichloride. By EBEN HENRY ARCHIBALD. WHILE aarrying o u t a seriea of elxperirnentg on the sollubility of potassium plstinichloride (Archibald Wiloox and Buckley, J . Amer. Chem. SOC. 1908 30 747) it waa ndiaed thart this salt undelrgoes hydrolysis. in aqueous so;lutJons at the ordinary tempera, ture. Some time latter while1 studying the conductivity of solme pla8tinum colmpounds (Archiba,ld and Patrick ibid. 1912 34, 369) it was found that this hydrollytic dwoimpwibion proceeded much mars rapidly when the solutions were exposed to1 the act'ion of light. As the extelnt ta which this reaction has tlakeln placw is any giveln time1 oould be measureid velry accurately whilst the rate ajt whioh it prolaeiedeld was suffiaiently slotw to1 allolw off a number of meaaurement8s being made with any olnel solution-a coadition thah ia satisfied by velry few inorganic salts-it was thoiught worth while to make a sonmwhat extended study obf the hydrolysis of this salt under diffelrent aolnditiolns as tol (1) dilutioln; (2) the presence of other chlarida and neutral salts; (3) the reversibility of t h e reaction.Prmiow Obssrwatim cegading thk Hydrolysis. The adion otf light oln poltassium platinichloride appears to have been first nolteld by 8onsta,dt (P. 1898 14 25). Hei states that light has the same elffect on very dilute solutions of the salt as he1a.t. A sollutiw containing 1 past of salb in 10,000 pasts olf water beloame turb,id whelii helat8eld folr a.n holur oc two.He abseirved no effect i n the ca,w olf more conmntmra,tced sollutions and seems to have judged the extant of the rea,ctio,n from t,he appearance of the solution and the formation of a seldimeiit, considelreld ta be pla'tinum motnoahloride. It is of i n t e r s t heIra t,o reifelr to a letter of Sir John Herschel to Dr. Daahay writIten in 1832 (Phi$. Mag. 1832 [iii] 1 58). This letter st.ak that if a solution oif pla,tinum in nitromuriahio a.oid in which t.he exoess o'f a,&d has bmeen nelutralised by the addi-tion of lime t.his being folllolwwed by filtration is mixed with water in the dark no prelcipita,tion takes pla,m folr a vary loag while, but if t<he mixt<ure is exposed to sunlight it instlantly beoomes milky a,nd a copious preloipitafs forms.The writer of the letteir further shotwed that this elffeot Wafs confined to t,hs vioilet end of the spe&rum no1 aation t(aking place when t u b e cont4aining th PLATMUM BALTS. PART I. 1105 platinum solutions were immersed in reid- or yellow-oolourd solutions and tlhen expomd t o the sunlight. Thab light greatly acceIerates the hydrdytlia decmposition of platinum tetrachlolride seems to have been genelrztlly remgnised. Kolhlrausch found that the conductivity oif aquelolusi solutions of this compound increiaseid muoh more rapidly wheln undeir the influence of light than when kept in the dark. The presence of the platinum eleictroldes also inurelased the veloicity olf tlhe reaction. Solutions od chlorolpla8tinic acid motre croaoentrateid than N / 10 were apparently not affected by light.EX P E R I M E N TAL. Pwpamtiom of Mat erkls. Hydrochloric A&d.-The hydrmhlosia acid used was prepared by heating concentrated Izydroluhlolria acid and passing the libera8kd gas into distilled water the first and last parts olf the distillate being rejedxd. Potassium ChZo.ride.-Coxnmercial potassium chloride was re-cryst allised selveraal times from water saturalteld with hydrogen chloride finally from pure wa,tm. Pdrtions so obtained were washed free of mother liquor and dried a t al high tempemtme. Potassium P%c&nichlm.de.-Tn preparing the chlolroplatiniu acid from which the platiniohlocride wag obt'ained platinum scrap was frmd of surfam impurities theln bolileld for some tJme in conoen-trabld hydroichloricl acid.The platinum wa,s thela dissollved in aqua regia land the solutioa evaporated almost tol dryneaq after adding colnceintrated hydroohlolricl acid. After again adding hydcro-ohlaria acid and evalpporating a second time the residue was dis-solvsd in water containing hydrolchloric add and the! platinum preicipita;t;eld from this by adding a solutioln olf ammolnium ohlaride. The resulting ammolnium platinichloride was colllsated in a Goloch filter washeid with aluohol and watlelr and dried in an air-ba,th a% a low termpera(tlure. The dry salt was then reduced by heating in a current of hydrogen and the platinum-black folrmed was well washed in watm. In mder to ensure the absenue of any nitrio aoid from the final prepara,tion the platinum-black was dissolved acaording ta the melthod suggehd by Webelr ( J .Amer. Chem. SOC. 1908 30 29) and modified by the author (Zeitsch. amwg. Chem. 1910 66, 169). Aumrding to this method the plat.inum-blaok is ma8de the anode in the lower past of a glass tube aboutl 2 m. in diamelter, containing conoenttrated hydrachloriu acid as edeotrolyte. At the a ' n d e the uhlorine ailtacks the platinum forming platinum chloride, and the remlting ohloroplatinio acrid falls to the bottom and oa 1106 ARCRIBALD TRE HYDROLYSIS OF be drawn off through a siphon sealed to the bottom of the main tube. The sollution prepared in this way is somewhat diluted and the platinum then precipitated by adding slowly a solution of a polrtion of the purifieid pokassium chloride.The precipitated plaltiniohloride a f h r being washed and dried is ready folr usel. A p a r a t us. The graduatiolns on the pipettes and buret,tes were tested by welighing the1 watelr delivered allowanoe beling made for air-dis-placement and the temperature! od the1 water. I n the case of the flasks a graduation mark was made a t thatj point on the stern a t which the flask coat8aineld waiter sufficient to balanoel brass welight8 equal to1 the apparent weight of a kilolgram or 100 grams as tlhe oase might be of water weighed in air a t 20°. The weights welre correlctad by the melthod suggested by Richards ( J . Amer. Chem. Soc. 1900 22 144). M e t h d of Meamring the Extent of the Hydroltytic Actims. As hydrochlorio aoid is formed as the hydrolysis proceelds the rate at which the reaction takm place and the extent to which it has prooeeded a t any given time can be measure!d by titrating a known volume of the solution with a standard solution of an alkali such a5 barium hydroxide.Among selveral indicators tried, such as methyl-red methyl-mangel coohineal and phenodphthalein, none appeared superior tlo phenolphtbarein. The mlour relaktion with this subsitanoe was distinct and delicatel. With the b u r e t h employed in this work the error in reading the volume delivmed did not exceed 0.02 c.a. and this with the stlrength of solution employed as standard corresponded with 0*0000078 gram of hydrogen chloride. K,P t C1, - ~ = 4 - 8 6 4 grams The solutions first studied contained K,PtCl K2PtCI K PtCl ____- 4oo 1.216 grams and -2d - 800 - 2oo - 2.432 grams ~ -0.6080 gram of pottasium platinichloride in a litm of solution.In terms of e'quivalent gram-molleculee od platinum chloride they were rapeotively N / 2 5 N / 5 0 AT/lOO and N/200. These solu-tions were prepared by weighing the required amount of salt in eaah case; the nesessary wahr was added in the dark and the solution caredully protleoteld frotm the light until everything was in readiness to begin EL seriw of measurements. The velocity olf the hydrolytic readion was so lolw eveln fm the most concentratad solution studied that the1 time rsquired tol dissolve the platinum salt need not be considered in any of the measurments. Th PLATINUM SALTS. PART I. 1107 initial audity was now measurd-this was seldom equivalent to more than 0.05 0.0.of the standa'rd for a 10.0 0.0. portion of the phtinum solution. The velsrYeils containing the soluttions welre then immersed in wate,r-b,a,ths conta8ineld in glaw t,anks and here exposed, ah a certain disttanael to1 $he radiations frolm a 300-wa8t;t laamp. The tempelra,tizre of t'he bath was ma.intlained const,ant. witihin 0*5O by means off a system of tubee through which water circulated. An ammetelr reading tol 0.001 ampere was placed in series with tBei lamp and by means off a volltimelter tbei elnergy bedng used was measureid a,t frequent intervals. Frolm time t o tdme 10 C.U. por-tions of the plattinurn solutions were withdrawn by means of a pipet.ts and the acidity was tltrated against the stlandard dka81i. The results olbt,aine:d for the abolve fonr solutions are givein bellow.The figura in the first wlumn indicab she time in minutes, during whioh the solution has been exposed to1 the light. The seoond column sholws the number of C.O. of alkali necessary to neutlralisei a 10 0.0. portion of the platinum solution. The third column cointaJns the weight. in grams of hydrogen chloride formed in 100 0.0. of saluticm. TABLE I. N/200-K2PtC1 SoTzition. I N / 100-K2PtC1 Solutiom. Time, minutes. 5 20 40 65 125 215 265 400 580 945 1736 2200 2900 B4OH), solution C.C. 0.04 0.10 0-14 0.20 0.32 0.54 0-64 1.08 1-72 2-34 3-06 3.30 3-35 HCl. Gram. 0~00015 0.00039 0-00054 0.00073 0.00125 0~00210 0.00249 0.00421 0.0067 1 0.009 13 0.01193 0.01287 0.01365 Time, minutes.40 60 125 240 430 1035 1630 1910 2050 2400 2700 Ba(OH), solution C.C. 0.27 0.32 0.51 0-84 1-53 4-04 5.24 5.68 5.86 6-36 6-46 HCl. Gram. 0.00105 0.00125 0.00199 0.00328 0.00597 0.0158 0.0204 0.0222 0.0229 0-0248 0.0252 Time, minutes. 40 125 265 410 580 955 1455 1810 1900 2150 2750 Ba( OH 12 solution C.C. 0.20 0.40 0.74 1.34 1-92 3.00 3-96 4.14 4.20 4-24 4.29 HCl. Gram. 0.00078 0.00156 0.00288 0.00495 0.00749 0.01174 0.01644 0-0161 5 0.01638 0-01653 0.01 673 Time, minutes. 40 60 125 240 430 1035 1630 1910 2280 2600 Ba(OH)2. solution C.C.0-32 0.42 0-68 1.10 1-88 6-46 7.24 8.12 8-56 8-70 HC1. Gram. 0.00125 0.001 64 0-00265 0.00429 0,00733 0.0213 0.0282 0.031 7 0.0334 0.033 1108 ARUHIBAJiD THE HYDROLYSIS OF These resultsl show thab the different solutions read a condition olf elquilibrium. in almolst the same time. The N/200-solutioln attlaine a condition of maximum acidity some two or thrm hours after the modt colncentratmd one. I f we calculahe the percentage of clhlorine that has been set f r w from the pla,tinwn salt wheln equilibrium has hien reached we find t'hat for the four solutions tlhe values are beginning with the mmt FIG. 1. 9.00 8.00 7.00 x N 3 6.00 3 6-00 $ .$ ,.$ 4.00 5 + 3.00 CJ 2.00 1.00 d % T h e in minutes.dilute solution 74.7 45.8 35.2 and 23.2 pelr cent. of the chlorine present as platinic chloride. The relamtiomhip between the time and the progrew of t'he reae tioln is belt,telr sholwn by the curves bcf Pig. 1 where1 times are plot-ted as absaissze againstl vollumes of ba.rium hydroxide solution used for the tlitratioa. The first pa,rt of the aume sholws nearly a stttsaight line tha.tl is, during the gelriold that t'he first thre'el-fifths od the reaction is t'aking pla'm indioating tha,t the hydrolys'is goes on a,t a,n almost oonstlant rats fofr a oonsiderab,le period of time. A velolcity-constant for this part olf the reatdim may tlhen be adoulated by dividing th PLATINUM SALTS. PART I. 1109 Time of expbbtll'e for solution N/iO0, minutes. BNCH) - solution C.C.At 20 cm. At 40 cm. I 0.16 35 125 0.24 50 265 0.40 126 410 0.64 205 580 0.94 315 955 1.68 515 1455 2.12 640 1810 2-92 925 2370 3-48 175 3165 4.00 500 4105 4.16 860 6686 m o a n t of hydrogeln chlotide fotrmed by the time and multiplying by t8he dilution. There is an indicatioln in the oaxe 04 the two weaker sollutioas of wha8tl Gooldwin (Zeitsch. physikal. Chem. 1896 21 1) has tomeld an induction period during whiclh the reaotioin prmemds very slofwly. This would suggest that solme substmce may be f oming-a produot of the reaction-that ca,balysea the remtioln during its later stag-. This point can be discussed tol better advantage when considering the reaction that takes place in the dark. I n order to show that the rate of tlhe reaction is proportional t o the intensity of the light folr a given source of light the folllorwing melasurments were! made for N / 100- and N/200-solutione placed at a distance of 40 an.from the source. The temperahure and otthelr fa.doas we're maintained the same as in the previous me8asureime8nts. N/200-So~Zutiort at 40 cm. I N/lOO-Solution at 40 cm. Time, minutes. 220 405 585 950 1741 2472 3195 4010 5135 Ba(OH), solution C.C. 0.14 0.28 0-48 0.76 1-44 2.24 2-56 2.70 2.84 Time, minutes. 125 265 410 580 955 1455 1810 2370 3165 B4OH), solution C.C. 0.16 0.24 0.40 0.64 0.94 1.68 2.12 2.92 3.48 Folr the sake1 of comparison we1 niay selt dotwn opposite the vollume of hydroxide solution nelcessary for the1 titration the time! during whiah the solution was elxpolsed; the correispolnding time for the sollutioas elxposetd a t 20 m.dist8aiioe is a3so sholwn in the t'able, these valuea being t a h n from the curves of Fig. 1. TABLE 111. Ba(OH), solutioh c 0.14 0-28 0.48 0.76 1.44 2-24 2-56 2.70 2-84 2.92 Time of exposure for solution N/200, minutes. F 40 220 loo 405 188 585 300 950 510 1741 870 2472 125 3195 280 4010 460 5135 555 5665 .c. At20cm. At40cm 1110 ARCHIBALD THE HYDROLYSIS OF These resulb show that at the beginning of the hydrolysis the rate of the reactioln is approximately proportional to the intensity od the light. However after the reaction has promeded a aertain distmaetwheln about one-tenth of the toltal amount of hydrogeln chloride has bean formed-the rate od tho reaction for the solution at the greater distance is more rapid t*han the1 intensity law would predict.This is perhaps to be expectled if the l a t m stages of the reaation are influelnced by a prolduct formeld during the hydrolysis. It is worth noking thatl this change in rate occurs when practically the same amolunt od hydrogen chloride has befen folrmed in eiach solution. The final equilibrium point is apparelntly not affected by a change in the intensity of the light as the1 titration is almost ide1ntiaa.l in the two oases. It will be of i n b r a t to recolrd a t this point tlhe behaviolur of mlutims of 'the platinichloride wheln made! up and kept in the dark. The solutions were protected from the1 light by wrapping the container in black paper and then enclosing it in a thick wooden box blackened within and without.The following tables will show the1 r e d t s of them obselrvatiolns. I n the preparation. of the N/25-solution the water had belen very oarefully distilled and bailed again just before using. The salt1 had been kept in the dark for several days bedorel making up the solutions and every precaution was taken ta exclude light both while preparing the solutions and after. The volumes of solution and weights of hydrogen chlolride are expremed in the1 units used before. TABLE IV. N/ 25-K2PtC1 in Darknew 1 N / 50-K,PtC16 in Barknew. Time, hours. 68-3 162.0 354-0 546.0 937.0 1120.0 1440.0 1775.0 2177.0 2515.0 2735-0 3090.0 WOH), solution C.C.0.06 0.12 0.28 0.60 1-52 2.04 3.04 4-94 7.14 8-13 8.46 8.65 HCl. Grams. 0.00023 0-00047 0~00110 0.00236 0.00592 0.00796 0.01185 0.0 192 7 0.02785 0.0317 0.0330 0.0337 Time, hours. 68-3 162.0 354.0 546.0 1625.0 2455-0 2755.0 3662.0 4850.0 BWH), solution C.C. 0.04 0.04 0.04 0.04 0-28 0.44 0.84 1.64 6.04 Ha. Gram. 0.00016 0.00016 0.00016 0-00016 0.001 10 0.00173 0.00330 0.01177 0.02355 In the cams@ of the N/100- and N/200-solutio;ns the're was no indiaa.tion that hydrolysis had even stlarteld after t$hey had been in the dark for six months. For the N/25- and N/50-solutions th PLATINUM SALTS. PART r.1111 results were as indicated. I n the la4tltm case the hydrolysis had not proceeded fair enolugh to bme. measured until approxima,tely thirty days had elapsed. For the N/25-s,olutJon the rea,atioa had proceeded t,o such a,n extelnt that itl could be detected a,t t'he end od five days. The ourves of Fig. 2 obtained by plotting the results of table IV sholw much more dist?inctly the cha,ra.ct.er oif tthe " induction " period. This period become6 motre' elxte8ndeld and exaggera,bd as t<hel solution beloo,mes mom dilute until f o r a sollu-tioln as dilute as N / 100 na hydrolytic decomposition wha,tever t,a,kes place over as ext'endeld a peiriod as six mont'hs. It appears 8-00 7.00 3 3-00 0: CJ 2.00 1-00 FIG. 2. 0 0 0 0 0 0 0 0 0 0 d G . I e 4 c * I c c ) m * 0 0 0 0 0 0 W W e a ~ O P .l ~ Z ~ 8 h u 4.00 3 3.50 .$ 3'00 h N v 3 0) s 2 50 * 2 Time in minutes for reaction in light in hours for reaction in dark. strange perhaps that the more dilute solutions are1 the more stable. The aonmntlratioin of the hydrogen a,nd hydroxyl ions has evidently little to do with the progrws of tlhe reaction although it might be argued that these factors are1 practically mnstant for the different sollutions the propoirtJon of water tol salt being so large for all concentrations studied. The time required for the N/25-solution t o reach an equilibrium point in da,rkness is approximately on0 hundred timB as long as when exposed to the radiatioas of the 300-watt lamp. F o r the N/50-sollutions the difference in time is somewhat greater.It weans possible that for the molre oolnmntratmd sollutiolns 1112 ARCHIBALD THEl HYDROLYSIS OF suffioient although perhaps an exwedingly small amountl of some substance-perhaps an hydroixy-salt-is protdumd whein t,he salt is first dissollved to clatalysel the hydrolyticl relaction and in the case of the N / 25-solution tlol give the1 reactiotn an appreiciable vellooity almoet a t the beginning. The shape1 of the curve8 oif Fig. 2 is thea more easily undeirstootd. The steep parts shosw tlhe acoeler-ating elffelct of the oatalyst in the absence of any effective radia-tJoins in al very stsiking way. For the morel dilute solutiolns this oaltalyst is noti prolduceld in colnaelntratiolns high elnough to affect the proigras of the reaotion.The Reve,rse Reaction. On teeeting the soilutJons tor deltermine whether the relaction could be drivein in the opposite direction it was folund that whein poltlassium chloride soldium chloride or hydroahloric acid was added tol a hydrolysad solution the reaction prolueedeld in the opposite direction either in the da,rk olr in the light the extent to which the reverse rewtion tolok plaaei delpending in thei oase oif any olne sollutlicm on the amount of chloride that had beieln addeid. The rate a t which the reverse reactioa prolwelded was very muoh slower in the dark than in the light? as melasurements given bellow will show. The efffect of platinum-blaok on the rciaotioa wa's also studied as s e t forth in the tablee. For this purpose a stlrip of phtinum foil was covered elect~rolytically with platinum-black and this strip afte'r beling thoroughly washed was immerseid in the solution to bcr studied.TABLE V. Relvelrse Reiacltliolns in Light N / 100LK2,PtlC1 Solution. Time, minutes. Initial 65 95 255 430 620 775 1305 2070 2660 N / 10-KCl. Ba(OH), solution C.C. 4.2 9 3-40 3.08 2.28 1.50 1-16 1-04 0.82 0.60 0.56 HCl. Gram. 0.0167 0.0133 0.0120 0.0089 0.0059 0-00452 0.00436 0.00320 0.00234 0.00218 Time, minute. Initial 20 245 385 700 1175 1775 2665 NI20-KC1. WOH), solution C.C. 4.29 3-90 2-56 2.06 1.62 1-26 1.16 1.10 HCl. Gram. 0.0167 0.0152 0.00998 0-0080 0.0063 0.0049 0.0045 0-004 PLATINUM SALTS.PART I. 1113 TABLE V. (comtinued). N / 200-Ii2PtC1 Solution. Time, minutes . Initial 65 95 255 430 620 775 1305 2070 4850 6600 N/lO-KCl. Ba(OH), solution C.C. 3.35 2-86 2-74 2-06 1.70 1-48 1-34 1.04 0.92 0.59 0.52 The reverse rea.ction HCl. Gram. 0.0131 0.01 12 0.0107 0.0080 0.0066 0.0058 0.0052 0.00405 0.00359 0.00230 0.00203 Time, minutes. Initial 35 185 385 810 1205 1775 2323 4850 5600 N / 20-KCl. WOH), solution C.C. 3-35 3.00 2.54 1-98 1.46 1-24 1-12 1-06 0-86 0-70 HCl. Gram. 0.0131 0.0117 0.0099 0.0077 0.0057 0.0052 04044 0.004 1 0.00335 0.00278 is ma t o tta.ke pla.ce at a compa!ratively rapid ram& a't the beginning the amount of change beling grela,t,er hem i n a given time t.han for the direlot reiaotion.This; is na doubt beca'use the added salt has so greatly increased the conmn-tra.tlioin of the chloirine ion. Towards the elnd holwever tGhe pro-g r a s b,eiooma very slow with the result that the time relquired for the reverse action to go to complelt'ion is muoh greabr thaa the time nelcessq for the hydrolysis t,ol t,ake p1a.w. I n the cams@ of the N / 200-pla8tinum solutions t'he time relquired for the reverse relactioa. is much greaher t'han for the N / 100-solutlions. The latter st,a.ge od the relaotioln for the N / 100-potassium platini-chlolrideN / lO-pot,assium chloride solutioln is complicated by the f a,ct thatti 8,s the potassium platinichloride is rsgenelrated the solu-tdon h o m e s supersaturakd wit$ reapeot to t-his compound and it orystdIises otut to a slight extlelnt.This probab,ly explains the croissing o f t[he curvels for the N / 10-potassium chlolride solutiolns as shown in Fig. 2. This also goes to show tha.t the hydrollysed salt is slightly more soluble in polt,assium chlolride solutioas than the normal oompound. If the r a b od the! revelme rea,ctioa is expreissed a,ocolrding to the usual formula using t,he relsults of the mela.suremeats say for the N / 200-potassium pla,tinichlorideN / 10-potassium. chlolride solution, a colnstlant is not obtaineld. The expression for a unimohular resotioa give6 a vadue which continua,lly diminishes whilst the bimoilecula,r formula yields ZL continually increasing number.The rels;ults of me,a,suremetnts made on solutioas reacting in the reverse direlatioln in the da,rk a,re &own below in table VI. The && of the addition of sodium chloride to the bydrollysed solution is also shown 1114 ARCHIBALD THE HYDROLYSIS OF TABLE VI. Re,verse Reactions zcrt Darkness. Potassium Chloride Added. N/50-K,PttCl,. NI20-KCl. I N/ZOO-K,PtCl,. N / 10-KCI. Time , hours. Initial 1.50 19-58 73.50 260.50 601.50 1101.5 1657.0 2540-0 3096.0 B 4 OH 12 solution C.C. 6.60 5.32 4.98 4.32 3.34 2-80 2.38 2.10 1-84 1.80 HC1. Gram. 0.0257 0.0208 0.0 194 0.01 69 0.0130 0.0109 0.0093 0.0082 0.0072 0-0070 ' Time Ba(OH), hours. solution C.C. 4-25 3.22 49.25 2-60 317-0 1.98 1973.0 1.10 3797.0 0.90 5957.0 0.72 8693.0 0.52 ~ Initial 3.35 HC1.Gram. 0.0131 0.0126 0.0102 0.0077 0.0043 0.0035 1. 0.00281 0-00203 Time, hours. Initial 317-0 1973-0 3797.0 5957-0 8693.0 49-25 Ba(OH)* solution C.C. 3.35 2.78 2.22 1-32 1.12 0.92 0.74 HC1. Gram. 0.0131 0~0108 0.0087 0-006 15 0.00437 0.00359 0.00289 S0diu.m Chloride; Added. N/200-K2PtC1,. N / 10-Na8C1. I N / 200-K2PtC1,. N/ZO-NaCl. Time , hours. Initial 48 75 1732 3556 5716 8452 12300 Ba(OH), solution C.C. 3-35 2.62 2.42 1.34 1.10 0.86 0.50 0.29 HCl. Gram. 0-0131 0.0102 0.0094 0.0052 0.00429 0.00335 0.001 95 0*00109 ' Time, hours. Initial 48 76 3556 5716 8452 16828 20476 -Ba(OH), solution C.C.3-35 2.94 2-82 2.1 6 1.80 1.72 1-50 1.20 -N / 100-K2Pt.C1,. N / 10-NaC1. Time, hours. Initial 29 219 1296 2376 4488 Ba(OH), solution C.C. 4-29 3.98 3-42 2.52 2-16 1.68 HCl. Gram. 0.0167 0.0165 0.0133 0.0098 0.0084 0-00655 HC1. Gram. 0-0131 0*0115 0.01 10 0.0084 0.0070 0.0067 0.0059 0.0047 PLATINUM SALTS. PAB.T I. 1115 Thel% reaulte show that the reverse maation brought about by the addition of a soluble chloride to the hydrolyd solution o m -t i n u a in the absence of light until folr the more colnmntrated sohtfions much the same equilibrium point is maohad as in the oase of the same retaotion taking place in the light.F o r the more dilute solutions the la,tter equilibrium point is pa& the reaction continuing for approximately two yela'rs by which time the hydrolysis has. almoist disappeared. The aatalytia effelcrt of platinum-bla'ck on tlhe reverse reaction is shown by ths results set forth below. In tlhe first oaw the sollu-tions were exposed to the radiations from the 300-watt lamp whilst the second series of resultcr refers to1 the realchion taking place in the absenae of light. In each cam theae reactions were studied simult7anelously with solutions kept under exactly the same conditions except that no platihum-blwk was present. TABLE VII. Reverse Reacti,om with and withowt Platiwmblack. I n Light. N / 100-KzPtC1,. N / 20-KCl. With Platinum-black.I Wit.hcmt Platinum-black. Time, minutes . Initial 20 245 385 7 00 1175 1775 2665 Ba(OH), solution C.C. 4-29 3-90 2.66 2.06 1-62 1.26 1-16 1.10 HC1. Gram. 0-0167 0.0152 0~0100 0.0080 0.0062 0.0049 0.0045 0.0043 BNOH), solution C.C. 4-29 3.90 2.56 2.06 1-62 1.26 1.16 1.10 HCl. Gram. 0.0167 0.01 52 0~0100 0.0080 0.0063 0.0049 0-0045 0.0043 In Darkness. N/lOO-KZPtCl,. NI20-KCl. With Platinum-black. 1 Wit,hout Pla8tinum-blaak. Time, hours. Initial 2 19.7 1296.0 2376.0 4488.0 8376.0 28-75 BNOH), solution C.C. 4.29 3-72 2-84 1-80 1.36 1-14 1.02 HC1. Gram. 0-0167 0.0145 0.01 11 0.0070 0.0063 0.0045 0*0040 B@Hh solution C.C. 4.29 3-88 3.52 2.36 2.02 1.54 1.30 HCI.Gram. 0-0167 0.0151 0.0137 0.0092 0.0079 0.0060 0.005 1116 ARCHIBALD THE HYDROLYSIS OF It is apparent that the effect of the platinum-black is no4 great enough to show wheln the reladion is taking place at a redatively rapid r a I k before tlhe lamp but it is quite noticeable when the reasation is proomding slotwly in the dark. A few relsults will show the effect of the prewnw of a neutral salt such as poltmium nitlrate in the solution undergoing hydrolysis. The values from measurements of two so'lutioas are given. TAELE VIII. Direct Reactiom with Potassium Nitrate:. Time, minutes. Initial 100 175 350 465 665 850 1380 1775 2020 2650 3000 Be(OH)* solution C.C.0.00 0.20 0.40 0.78 1.00 1.44 1-86 2-66 2.92 3.04 3.28 3.44 HCl. Gram. 0.00078 0*00156 0.00304 0.00390 0.00562 0.00723 0-0104 0.0114 0.0119 0.0128 0.0134 -Time, minutes. Initial 100 190 225 315 605 800 1215 1776 2020 2650 3000 Ba(OH)!a solution o.c, 0.00 0.22 0.46 0-58 0.84 1-52 1.91 2.40 2-90 3.08 3.26 3.40 HCl. Gram. 0~0000 0.00086 0.001 79 0.00226 0.00328 0.00592 0.00745 0.00936 0.0113 0.0120 0-0127 0.0133 These raults show thah whilst the potassium nitrate has a, retlarding effelct a t tlhe beginning of the reaction the acidity of thei solution finally reaches just as high a value as in the a;bsmce of the neutral salt. The total time required for the ractioln to reach an equilibrium point is but slightly greater when the potassium nitrate is preaent.In agrement with the retarding effedl of the nitrate is the f a d tlhat the solution whioh contains the grsa4telr amount od neutral salt lags slightly behind the other. As stated above it appears from the results in table I that a substance may be formed from the hydrolysis which acts as a oatalyst of the reacbioln inoreasing the speed very perceptibly during tlhe first half of the decomposition. This polint was further tested 51s follows. Two so1ut.ions were prepared in the same manner of equal concentration as regards platinum salt whilst one contained 1 C.C. of dilute hydrochlolrio acid. They were then exposed at the same temperature and at the same t h e to the radiations from the lamp at equal dishanax frolm the source.Measurements of the aoidity of $he solutions were then made at frequent intervals. The results failed to show a,ny acm1era;ting influence whatever on the part of the hydrochloria acid. Th PLATINTJM SALTS. PART I. 1117 reactioa ne:cewarily did not proceed so far in the solution co,ntaining the; added chlolrine ions but t'his was the olnly eiff elct noltimd. Anoher axperimeat with the same object in view was madel as follows. Two1 sosluttion od t'he pla.tinum salt were prepared one N/100 the other N / 4 0 0 . These1 welre exposed to the light until p d l y hydrolysed then pla,cejd in t'he da'rk. The acidity of the molre mnce8ntIrakld sodut.iojn wa,s melaaured af t'elr twenty days and the me'asurement sholwwed that the hydrollytic reaction had a n -t,inueld until the usual equilib,rium polint hamd been readhd.In the aase of the N/400-solution a measuremeat was made after thirty days b,ut the rise1 in acidity i f any wa,s so small thab it could not be detected with certainty. After thirtyeight days more the result of another measuretment indicated that the hydrolysis was promled-ing b,ut very slowly. A 10 C.O. port.ioln which neut,raliseld 0.88 0.0. of aJka1ina sollutioln when first plaroe.d in the dark now required 0.98 0.0. The nelxt tlwa months b,roaght no pelrcepltible change in this so;Iution and sixteen niolnths aft.elr it ha'd beeln placed in the dark a 10 0.0. porkion relquiretd olnly 1.10 C.C. of hydrolxide sollutioln. Ano,t,helr N/$OO-solution made up at the same time as this me' but nevelr exposed to the light showed no1 indication of any hydrolytic atation after sixteen molntlis.It would selelm as if a certain con-ae.nt8ra.tion of the catqalytlic relageinti was necessary before the hydrolysis will promeld. In the caw of tlhe N/4OO-solutlon that had been exposed to the lightl t'his coaaentration had apparently just b e m ma.ched befo'rei the d u t i o n was placed in th.e dark. It wa.s not elxpeotefd t'hah the acceleirating influence of p1a.tinum-black woluld be suffic:ieiit'ly grelat t'o bje noticed in a soIlution undelr-going hydrollysis b3edoIre the1 light. It wa8s tlhought wojrth while, however to memure this elffect on sollutIolns rea,oting in the dark. Accolrdingly two solut8ions were ca,rrsfully prepared ela$ch N / 25.In one was placed 0.05 gram od pla,tinum-black. B d h solutions were placed in the dark and me'asureld from day to day. After three days 10 C.C. of one solution neutrahed 0.06 off dkali solu-tion whilstl the1 same1 volume1 of t.he one cmhining the platinum-blauk required 0.25 C.C. After five days the oorresponding voluma o,f a.lkali solutlion were 0.06 0.0. ahd 0.45 a.0. The effelat of the platinum-black was very evi delnt bolth in stasting the hydrollysis and in acmlelra,ting the reactioin. Anot'her expelrimelnt almost idelnticaJ wit'h bhis one wits made by a,dding 5 C.U. of an N/25-solution conipleltelly hydrolysed tlo a nelwly prepre'd N/lOO-solution and pla<oing this in the dark. The relading for a 10 a.a.portion of t.his sodution wm now 0.98 0.0. 09 alkali; after two months tqhe vollume of a1ka;li required for a 10 0.0. pmtion was 2.32 ox. showing that a sufficient ammnt o 1118 ARCHTBALD THE HYDROLYSIS OF the a8cmlelrat8ing sub,stame had bwn added to cause the hydrolysis to take place. The efielct of the1 tmpelrature oln the rake of tlhe rsaotim and t,hel extelnt of t,he hydrolysis rsceiiveld some attention. It was first asmrt8aineld wheltlhelr a sollutim which would not undetrgo hydrolysis in t'hhe da'rk a(t t'he olrdina,ry tempera.tnrel woald hydroilyse if kept a t 80°. An N/lOO-solutioa was te#st'eld in this way. The titratioa for a 10 0.0. portion of this sollut8ion was 0.04 0.0. at ZOO. After being kept in the dark a t 80' for three hofurs the aorresponding tit.ra,tion was 0.16 C.C.On cololling to 20° still in the1 da.rk the titra8tion fell to1 0.08 C.C. After being kept in tlhe dark a t 80° fo'r a,nother periold of thr'ee holurs a 10.0 C.U. polrtion aga,in requireld 0.16 U.C. of a(lka1i. I n the1 a4bs.elnce of light the t,e,mpera8ture has little i f a.ny influeam o a the! hydrolysis. The1 same1 conclusion is drawn from a' colniparison of t.he rate od the1 retactlion taking place a& 25O with that1 a t 35'. The1 va8riatloln here is only manifest towasd the elnd of tlhel relafotion wheili the diffelrelncel in the1 elquil-ib'rium point-a grelatelr degre'e od hydrolysis a,t the higher ternpelratnre-is sufficieatl t'ol shomw in tho fina,l reatdingsf. For the purpose of ascelrtaining to wha$ extelnt the1 hydrollysis would be inmease'd by al rim in tempelra,tare t'hreel solutioas welre elxpowd to t'he radiatdons of the 300-waftt la.mp at a.dist.anae1 of 20 an. the wafelr-ba.th beling maSntained a t the temperature shown bellow. From time to timel 10 C.U. portiom of t,he platinum s o h -tlions were withdrawn aad tJtra,te,d t'he light being continued a.t a,ny one temperature until equilibrium ha'd beefn a,tt&eld. TABLE IX. EfJect of Temperaituse om the Hydrobysz's. N / 100-K,PtCl,. I iV/50-K2PtCl,. 1 N/25-K2PtC1,. Tem- Ba(OH) HC1 pera- solution (100 c.c.). ture. C.C. Gram. 20° 4.29 +0-0167 50 5-24 +0*0204 80 5-90 +0.0230 Ba(OH) HCl solution (100 c.c.). C.C. Gram. 6.45 +0*0262 7-45 +0*0291 8.20 +0*0319 Be(OH) HCl solution (100 c.c.). C.C.Gram. 8.70 +0*0339 10.16 +0-0396 11-06 +0-0431 If we express the inorelase in the acidity of these solutions as percentages of the va,lues a t 20° we obtain the1 following coefficients for temperatures between 20° and 80° N/100 0.62 N/50 0-45, N / 2 5 0.45 per cent. These cmfficienta are notl very diffelrent for the1 several cIonmn-trations studied. From the amount of hydrogen ahloride formed a t 80° we find tha& for the iV/lOO-solution 63 per mt. of th PLATINUM SALTS. PART I. 1119 chlorine preaent as platinic chloride has bem used to f m hydrogea chloride. If we! represent by ohemiaal elquatioas the several stage@ of t h e hydrolyticr de~mposition of the platinum salt we find that for the N / 25 -solution the equakioa K2PtC1 + R,O = 2K’ + PtC&(OH) ‘I + H’ + c1‘ indiaaIkl pretty clotselly t,he eixtelnt t’ol which the1 hydrolysis hati taken pla’ce; whilst for the1 N / 50-so3ution t>he elxpreesim would represent morel marly the conditIion of the solution.When the solutions are as dilute1 aa N/100 olr N / 2 0 0 the rspelotive equa)tions would be and 2K$?tc16 + 3820 =4K’ + Pt,CI,(OH)” + PtGl,(OH)” + 3H’ -+ 3C1 K2Ptc16 + 2H20 = 2K’ + Pt~C14(OH),” + 2H’ + 2C1’ + 3HzO = 2K’ + Pt,C&(OH),” + 3H’ + 3C1’. The a h 0 equat.ions c’orrelspoad with a temperafure of 20°. At highelr tmnpera,tures t,he deoompolsitdon of the1 sa,lt is more ne:arly colmpleitq which is in a4gre80metntl wit’h the factl that when aI dilute solut.ion off thei pla,tlnichloside is boile’d in the light an insoluble substance is deposited. Obviously the possibilities of this hydrolytic a.ctim should be kept in mind when making a delterminatioa od poltassium by melamns of this salt; if a solutioln of the pla,tinichlo’ridel is b,eing elvaporahed, a suffioient amount of hydrochlorio a.cid must be preseatl to prevent the hydrolysis taking plaw whilst i f the salt is beling precipitated, hydrolohlolric acid must’ amgain be present to ensure1 the formation of the nolrmal compound. Pohassium plat8inibrolmide shows solme inhrest’ing felaturels not nolt,icelable in the oase of the platinichloride and it is holpeld to submit soon a oommuniaakition dealing with this colmpound. Summary. It has been sholwn tha8t solutions of potlassium platinichloride undergo hydrolysis when exposed t,o the action of light. I f the solution is as concelntrated as N/50 this hydrolysis will begin and will be completed in the dark; for a N/lOO-solution or one more dilute no decompoaitioa takes place when light is excluded. A subatIanm is formed by the1 hydrolysis which catalysee the reaction and will initiate1 the decompmition in a newly prepa6red solution. The addition of a soluble chloride tol the hydrolysed solutio 1120 JONES AND LEWIS: Oilusesl a oomplejte revelrsad of the relaction showing that the substances formed during the dired reaction are sohble. The reverse rewtioa is influelneed by light1 in muoh the same way a8 the dire&. The complelte reversal od a saluticm as dilute as N / 200 mquirels nearly tIwa ye8a8rrs. A neutrd salt has 8 slight reltarding effect on the dire& readion, bmut doee not influence the equilibrium polint. The accelelrating influenw sf platinum-bhuk on both the direct and reverse relaotions is quite noticelable when t7hew relactiam am takifig-place in the da,rk bat is not melasurable when light is atding on the sol ' u t' 10ms. CHEMICAL LABORATORY, VANCOUVER CANADA. UNIVERSITY OF BRITISH COLUMBIA, [Received July 23rd 1920.