REVIEWS
kiiitls of crystals separated spoiitaneousl!- from t h e supercooletl nielt. F:speririieiits were also riiatle with 140suhstaiices to tleteriiiiiie whether it \vas possible 11~-rapid cooling to coiiT-ert. theni iiito tlie state of glasses. The attempt p ~ ~ v e t l successful wit11 fifty-iiiiie of tlieie suhstaiices wit1 there is iio reasoli to siippose that this nuriiher might iiot lie iiicreaseti very largely 1 ) the ~ use of more effective riietliocls of cooliiig. 'The author iiicliiies to the lielief tliat. theoretically at aiiy rate, all liquids may be iriatle to pass at \vi11 either into t h e a r n o r p l i o ~ sor the crystalline state. 0 . B.
1v.
~ ~ ~ J O - ~ O 7 l / , h O l .YJ'.Yfel//S /t'Jl~
Heat of separation in solutions, lowering of the freezing-point solubility. -'The equatioii A , h / 2 7 1 / 5 . l b 7 k f . ATLJI. 64, p i (iS9~').
(wliich for dilute solutioiis is identical ivitli r>in't Hoff's foriiia1:i for t h e loiveriiig of tlie freezing-point) agrees well \\-it11ohser\-ations on solutions of o ! / -the eqiiilihriuiii constant for t h e benzene solution ant1 riiultiplieil hy the clistrihuticm coefficients of picric acid aiid $iiaphthol. The real gist of tlie paper is that P-iiaphtliol picrate is iiot :lecoriiposed 1,- heiizeiie with precipitation of either
component while it is cleconiposed h>-water with precipitation of ,?-iiaplithol This is referred very properly to the solubilities of 3-naphthol and picric acid in benzene and water respectively and to the electrolytic dissociation of picric acid in water. If'. TI.n. The equilibrium CO -- H,OZCO, -- H, and the study of explosives. C. Hoitseiitn. Zeit. Phys. CIIm/~.2 5 , 656 ( r S 9 S ) . - .kcording to Sauniann antl Pistor the formation of carbonic acid from carbon inonoxid and x a t e r can be detected at ahout 6oaOwhile thereversereaction does not take place to an appreciable extent until a teinperature of about 900' is reached. .kt higher tetnperatures the equilibrium slioul(1 be displaced towarcis the carbon rnonoxid side. Tlie author has taken a nuniber of explosives and calculated the temperature reached during the niotnent of explosion. He finds that the ratio of carbon inonoxid and water to carbonic acid and hylrogeii is greater the higher the temperature. The calculated temperatures ranged from about 2 10: to about 29m0. Tlie results are only approximate, the dissociation of carlmnic acid into carbon nionorid antl oxygen not 1jei:ig consirlereil in the calculation of the equilihriuin. It would seem a qliestioii. ho\\-e\-er,wllether there are not two equilibrium constants at lo\v temperature, Tliougli reference is made to the possibility of ' false eqiiilibriuni ', this is not really taken into account at all.
IC'.
n.B .
Investigation of the theory of solubility effect in the case of tri-ionic salts. ' 4 . A.-II\Oj'es niid H. Tt'oodwo?'t/i. Zeit. phys. C/te?u. 26, ~ j a foil?,. ; Alu. C h e t i ~Sot.. . 2 0 , r94 { rS99). - Deterininations were made of the solubility of lead iodid in pure xvater. in presence of potassium iodic1 and in presence of lead nitrate. The concentrations were calculated from conductivity ineasurenients, the migration velscity of lent1 a s ion being taken as 6S.3 at 2 j 0 . The conclusion drawn from the erperitnent is that the soluhility of lead ioclid is decreased by the addition of either lead nitrate or potassium ioclid in such a way that the product of the concentration of lead as ion into tlie square of tlie concentration IC'. . B. of iodin as ion reniaiiis constant.
u
Veiocif ics On the velocity of crystallization. F. 71'. A7itste?,. Zeit. phys. Clzem. 2 5 , 480 (1.898). --I criticism of Tarnniann's paper ( I , 749) because Taninianu assunied that the temperature at the surface hetII-een solid and liquid was that of the triple point. This is disputed on the ground that the system is not i n equilibrium. Ti/. D . E . On the velocity of crystallization, 11. C . T a / z m n x ? i . ZeEit. p/zys. Chetu. 26,307 (rY9P). - Kiister's claim (see preceding review) t h a t the temperature at
the surface between solid and liquid is not that of the triple point is looked upon 16'. D.E . as preposterous. The author's position is restated at length.
B lect 1.0 1i ~ oitz'e Fo ries On theelectromotivebehavior of chromium. TI'. Hitto?f. Zeit. Pl7jfs. C/ie?n. 2 5 , j z 9 ; Ivied. A i i i i . 6 5 , 3 2 0 ; Zeit. Elektr.orhe~riie, 4,jRz (rS9S).-\Vhen chromium is made the anode in concentrated solutions of hydrochloric acid or in fused
RPi sicn 1s
451
cliloritls it dissolves as chroiiious cliloritl CrC1,. IYlien aiiotle in dilute solutions and in fused salts of oxygen aci Is, it ilissolves as cliroiiiic acid anti is liesavalent. This can lie statetl more tlefinitelv. \Vlien a halogen is set frce a t t h e a n o ~ l etlie cliroiniuni is liivalent, corre pondirig to the ositl CrO : ~vlienorygeti is set free it is liesavalent, correspoii~litigto tlie ositl Cr(>,,. W i e n anorle i n alcoholic zinc chloritl it is trivaleiit, Cr,C1, being formed. \Yhen chroiniurn dissolves as chruniic acitl. it stands iii t h e voltaic series l)eIo\v i n e r c u r ~:- xrlieii i t tlissol\-es as cliroriious clilorid it stai-(ls just helow zinc. The "inactive chroiiiiuiii is believed 1 ) ~ t-h e author not to he ilur to t h e presence of a n iiivisihle film of ositl. "
ii/'.
zj.
,z;
Studies on the electrolytic decomposition of aqueous solutions. L , (;/trscr. Z~/~.fifi.ui./it,riri~ 4,, , -735, 373. 357, 4z-f [ iS5S I . -The chief object of this paper \\-as to clear u p tlie tliscreliancy lwtxveen t h e electromotive force of the gas cell. I .OS volts. :m(l tlit. polarization value for the clecoiiipositioii of n-ater. 1.6; volts. Tlie mean value fur a series of gas cells 77-as r.oSo volts xvitli acidor hase-. I Y i t h tiortrial caiistic pt:isli the vnliie was ahout fix-e millivolts liiglier, T h e teniperature coefficieii t with sorliuin liytlruxid as electrolyte \!-as n.oor4; as list ~ . ) , c o 1 ~f 1o 6 ~ u i d1 1 ~ !;;tiale. . Increasiiig tlie concentration of the electrolyte raised t h e electrotrioti\.e force. tliougli not to t h e atrioiint required hy tlie theory. Other solvent.; t h a n \v;iter \\-ere trietl, lint were uinwtisfactory o\viilg to perositl rleconipositioii nt oiie or tlir other of tlie electrotles. -1tltliiig h~-tlrogen t o ail aqiieous acitl solutioii in sinal1 qiimtitiei raisetl tlie electroiriotire force : addetl i i i larger quaiitities it retluccd it to almut 0.S24 volt. I n the polarization exrlerimeiits a sniall &ect \ v a s noticed at aliout 0.j - 6 volts, a marked effect at I .',6-Svolts, a n d yet another at 1.6; volts. Tlie change a t 0.5-6 volts \vas more nixrke-drox~-l anrl oxygcii. Iii the gas cell ~ v have e a n 0. c.lectrotle alii1 oxygen goes into solution a s ion jiist a s zinc goes into s 11 as ion, The value
%,it.
-
-
To precipitate hytlroxyl requires 0.j 9 volt iiiore. g i h i g 11:: the regular \ - d u e of 1.6; volts, There l&ig little osygeii as ion in the ;olutioti relati\-ely to the liytlroxyl as ion. tlle tlccuII1positioii at 1.0s volts is necessarily T-ery s . and niay easily he ox-erlooketl. By using inagiiesiu~nsulfate iii one a n d coilcentratctl sulfuric :icirl in a iecoiitl. tlie author w a i able to fin( .9j volts a s the value a t \\-liicli I
.OSvolts represents the el-mination of
-
__
-
2H
ant1 0 .
-
211 xiid SO, separate while I I and HSO,require allout 2 . 6 j vults. This last \-:ilue is iiitercstiiig. coincitliiig a:, it tlcles. ivitli the ' ' iiiaxiiiiiiiii pol.el)lacing the liytlrogeii 1 ) ~potassiiiin gives 11s I . i o volts : by s;otliunn r , ; ~ , j \-(,Its. T1it.e figures refer tu iiorii:al *oliitio~is. I:or iiiorc coiicciltr:1tetl sol11tion. tliey are less. tliougli not to tlie exteiit reqnireil 11y the tlicor?.. \\-it11 s a t u r ~ ~ t e t l c d c i u r i i . stroiitiuiii, anti liariuiii liytlroxitl solutiolls. tlie fipu-es \\-ere 1.3:. I ,2 0 , atit1 I . I Si x-olth. 1:or a solution hatiirateti 11itli respect to nlclgnv*iuni Iiytlroxitl rnesiuiii sulfate. to \rhich a few drops o f cau.tic pot.1~11Iiatl heel1 ~~rlrleii. inpxitioii value \ v a s I . j g j volts. 11: D . 17.
Chemical equilibrium and electromotive force. C. A*uiil)fev. Zeif, fihyx. 26, 2 j j ; Zeit.E l ~ k f i ~ ~ c / i e i i4, i i j,iq e , ( r S 9 -The equilibriuin betryeen thalliuni clilorid and thalliurxi sulfocyanate has been studied chemically and electrically with refereiice to van 't IIoff's ecluatioii i~.RT log I< 7 . 39.9O. zo.oc, anti o.So the ratio o iloriii to sulfocyanate at e q u i l i b r i u n i ~ ~ a s o . S j , 1.24a i d 1.74 by clieriiical anal) wliile the values calculated froin the electroinotire forces were 0.37, 1 . 2 7 1 1.77 for one cell, and o.SS, 1.2jatid r.Sz for a second cell, tlie ratio of clilorin to suliocyaiiate heiiig about 0.84 iii the first cell and about 1.52 in the second. The cells were macle up T1 T / C K C l 1 I- heating the solution to j j ' - 6 0 ~ . adding a little conceiitratetl nitric acid anti a little alcohol I, to prevent foriiiatioii of perositl 1 and keeping the potential difference constaiit at I . 3 j - I . $ volts. There is no tlifficult?- in preciiiitatitig over a g r m i of silver iii six liours and the method has been used successfully iii aiialy~ingsilver coins. It'. 8.
u.
On oxidation and electromotive force. chciiiie. 4, 5-?4 ! zS9 carhoii dioxid was t h e \-a11 ' t
HOE
reduction cells and on the effect of complex ions on t h e 12. Peti>ix. &if. ~ I I J ' s . Cheiii. 26, ' 9 3 ; Z?eit. E l e k f r o -To bring the electrodes to the same value a ciirrent of uiitl very effective. One object of tlie paper was to apply
formula
-
F r log 11e
iu to
oxiclatioii aiid
reductioii
cells.
xyliere k is tlie equilihriuiii constaut aiid ii the ratio of the concentrations. The author considers tlie case of a two solution cell, one solution heiiig a mixture of ferrous and ferric clilorid, and the other the normal calornel electrode. The reactjoii m a - he Tvritteti H g Fe" CI' z ~ e . -. H ~ C L Consitieriiig HZ and HgCl as solid phases ant1 C1' as constant by definition \i.e shall have Ci a. C;;. I n the actual rrieasureineiits tlie ratio of ferrous clilorid to ferric chlorid varied froin I : 99 to 99.5 : 0. j. The resuits were given rvith great accuracy by the formula;; = h - -o.oj;s log Ci:L'/ Ci:;. The question of dissociation appeared to be of 110 importance. 011 the other haiid it \vas fouiid that ferrous sulfate i n solutioil lias a very differeiit reducing action from ferrous chlorid of the same nominal concentration.
453
Rcz '2'6s''S
The atteriipt t o apply i-aii ' t Hoff's foriiiula citiantitativel>- to solutions of cliroiiious ant1 clironiic salts or of rriaiigaiious m i d manganic salts was riot very 1. One iiiterestiiig poii:t \\-as noticed. .\cicl sol,bitions of clirorrious ve livdrogeii ~ l i e i iii i coiitact n.itli platinum. .idtliiig sodiuiri iluoritl to a solutioii of ferrous ant1 ferric chloricl iiicreased the reductio11 poteiitial very inuch ai:tl this \vas .ho\\-n to be d u e to t h e formation of a complex salt, xliich wcis o1)toine:l crystallized a:i Sa3Ft 0. I FeC1, 11yo.;-o.l \-olt. if t h e difference is t o lie attributed to the relative tlissocidtioii i i i tlie two solutioiis. I17. D . C .
On the dependence of the electromotive force and the efficiency of the lead accumulator on the concentration of the acid. F. I l o l c ~ n l ~ k .A-ii'. ~ ~ : ' i ~ , i ; f i . o r / r c , i i z i L ' ,4, 349 ll'icd. Airir. 65, S,# (iSy - The Heliiilioltz furniuin for coiicciitratioih cells without tliffusioii has I)eeii applied to accuriiu1;itors Tt-itli different coiiceiitratioiis of sulfuric acid. Tlie vaporpresswe (lata \\-ere t a h i i from Ilieterici's nieasurernents. The agreeAissuiiiitig tileiit l)et\\-eeii theory ant1 experiiiieiit is very satisfactory. that tlie reaction iii the accuniultitor is represeiited 1))- t h e equation 1'bO2 - 1% zII,SO, z 2 I ' b S O , - 2H,O. t h e author lias cnlculated the electromotive forces 1)y itie ins of the Helmholtz foriiiula for t h e relation airioiix electroiiiotive force. heat effect and teinperature coefficieiit. Tlie heats of dilutioii w e r e taken from Tlioriiseii's iiiensurenients aiid Streintz's data for the temperature coefficient were used. Tlie calculate11 results (lo not agree with the espeririieiital (lata as closely as i i i the preceding case ; hut this is attrihuteti to the iiiaccuracy of t h e figures on 7.vliicli tlie calculatiuns \\-ere basell. I t ma>-he iiiterestiiig t o record that the el'xtroiiiotix-e force of tlie accurnulator varies from I . S Z to 2 . 2 9 1-olts as tlie coiiceiitratioii of tlie acid cliaiiges irorii four to fifty-eiglit percent. 111t h e secoiiti part of t h e paper there is n Iliscussion of the causes affecting tlie efficiency o f the accuniulator. A s is well kiio\~-iitlir chief loss is due to the fact that tlie accuniulator is charged under a higher voltage tlian it is discharged. T h e reason for this is the c'iaiige of coiiceiitratioii at and niore especially iii tlie electrode. For a given cliargiiig current. a giveii excess uf \-oltage \vi11 be necessary in order t o ovei come the counter electroiriotive force. .Is first ap(.
~
prosirnation the author detluces tlie formula e
c B
~--
12t
volt-coulom1j wliere e
is the loss of energy. I t h e ctirreiit strength, t t h e time. k t h e me:m coiitluctivity of tlie acid i n tlie electrode, y a factor due to t h e niec1ianic:il structure of the plates ancl C a proportionality factor. It is assuiiietl that k is practically iiidepeiit1ei:t of I when t h e chargiiig atid discharyiiig current are equal iii streiigth
and t h e equatioii becomes e = KI't for constant curreiitancl e
--
!
I< 12&for vary-
iiig currents. I; being a constant characteristic of each accumulator. This formula (which is of great practical importance) was applied t o some published technical ineasiireiiieiits and gave quite satisfactory results.
1v. D . n. On the principle of the dropping electrode.
W. Ptr,!i~lnrr. Zeit. p/zys.
C h c m 2 5 , r 6 j ( z S 9 S 1 . -Seriist looks uy,oii tlie ciroliping and t h e stationary mercury as forming a coiicentratioii cell. T h e anthor lets the tip of t h e dropping electrode dip into the solution and finds that, for se\-eral minutes after t h e flow of nlercur~-has been checked. there is a potential difference 1)etween tlie two mercury surfaces. -111important feature of the paper is the tacit adniissioti that t h e dropping electrode does not perniit one to iiieasure siiixle potential clifferences. .\t t h e close of the paper the author outlines a proposed nietliotl for measuring single poteiitial difference that appears to involve reasoning in a circle. W. D. B. Elrcfm l j ~ s i s11 iid .E/ec-ti-olj~f ic Dissocio iioia Determination of dissociation constants from increased solubility. 15'. Loii'eiz/zerz. Z f i f .fi/ig,s. C / I P I I2/5. , .?.\Is ( I ~ C ~ ' ? ) -The . solubility of a weak acid
i n aii aqueous solution of a Tveak hase is greater than in pure water. If t h e dissociation constaiit of the acid lie kno~v-nas \!-ell as t h e dissociation of water, t h e dissociation constant of the lxise m a y he calculated from t h e increase in soluliility hy applying the mass law formula. T h e author takes I . 14 '>; ro.7 as g i r ing t h e reacting weights per liter of dissociated \\-ater. T o test tlie method the author trier1 tlifferent concentrations of aiiilin atid of p-toluitlin with saturated solutions of cintiarnic acid aiid of p-iiitrobenzoic acid. For atiilin he ohtained as mean values 5.6 ant1 5,sV TO-10 : for fi-toluitlin 20.; atid 20.5 h 10-10. By the coiitiuctivity rrietliotl Rredig,iouiid j . 4 > 10-10 for atiiliii a1itl 17.2 10-10 for p-toluidiii. L7siiigp-nitroheiizoic acid and $-hronihelizoic acid the ilissociation constant of nietanitranilin was fontid to lie 3.2 fi 10-12 and j . 3 w 10-12 respectively : that of p-nitraiiiliii was r . I \ 10-12 from t h e esperitnents wit11 t h e first acid and 1.3 'K IO-:^ for those with tlie second. (hvi11g to the slight solubility of o-nitratiiliti. the solution was saturated 71-ith respect to it and varying qiiaiitities of hydrocliloric acid adtlecl. The cliFsociatioti constant of o-tiitranilin \vas thus fuunti to lie I . j JL-ith ria-iiitratiiliti i n escess ant1 liydrociiloIO-14. ric acid a dissociation co:istant of 4, j y 10-12 vas f o u d , differing not at all If,?. n. 2:. from that obtained with a sparingly soluhle acitl.
>.
Experimental investigation of the dissociation of substances dissolved in ). aqueous alcohol. E. Cohcr2. %r,if. p / i j ' s . C / ~ L , I2I5/, . z ( ~ ' C q ~ q-Experiments were made with XI,KC1 and CH,CO,Sa. The alcohol had a conductirity of I.j 10-11 ; the \vnter of le55 tliall 0.24 . \ 1 0 - 6 at -1S3. It was f o u ~ i dinipossible to work at zj" p-ohalily liecause of oxitlation of the alcoliol in contact \vith t h e platinunl black of tlie electrodes : a t IS" this difficulty was not scrious provided the ~neasurenientswere not tilatie too h l o ~ l y . Special precautions ere taken i n diluting the solutions. T h e results of t h e inr-estigation were quite surlirisiiig. p'or each tiiisture of aqueous alcoliol tlie conductivity for a ~ i ycoiiceiitration of R gi\-eiisalt can he obtained by i~iultiplyingthe cotitlucti\-ity forthat coiicentration iii pure ater by a constant. This holds only for so1utioi:s contai~lingless A,
than sixty percetit of alcohol. This stateinelit m a y also he worded : I ' 111 dilute aqueous alcoholic solutiolis the effect of tlie amount of alco1i.il on the rnoleciilar con(luctii-ityis iiitlepenilei-tt of the coticeiitraiioti of the solution. " The author seeks the erplaiiatioii of t'iis very interesting theorem i n the hypothesis that tlie electrolytic conductivity is not an accur.ite measure of the dissociation : lie rejects the hypothesis that the a:ldition of alcoliol does not change the dissoci:ition, because 1;ahlukoiv anti Zacconi have fouind that the inversion velocity of cniie-sugu in dilute hJ-(rocli1oric aci-l is loirereil by the a:ltlition of alcohol. IVhiIe the conclusion m a y he right, the re:is~,!iing seems rwak. Kablukcw and Zacconi ohtaiiied a constaiit of 21.3 in \rater and of 16.66 iii fifty percent aqueous alcoliol. If we consider that the i-oluiiie coiiceiitratioii of the water has been increasetl one-half it \vo~il!lsee111quite rratonable to si!- that the presence of alcohol hall iiicreasecl tlie catalytic actiJii of the liytlrocliloric acid insteatl of reiliicin:;. it. IVhatever may he tlie esplanatiun o f the results, this paper of Cohtii's 1I: I!?. is a clistiiict coiitributioii to science.
u.
Studies on the electrolytic reduction of the nitro-group. IV. LOD. Z e i f . E / e k f r o c h e ? / t i e 4, , 323 ( T ~ T : A S ) .-The author has claitiietl iii the past that all et1 through iii the re:luctioii of tlie nitro g r m p and this paper ce iii favor of this view. The futitiarnental idea is that if oiie introtluces into the solution some substatice that will react \\.it11 oiie of tlie intermediate carnpouiids. tiit resulting product c.~:ibe isJlate 1 a it1 identifie 1. I n fortridtlehytle n-e have a s.ithst
