Allen, Herman Camp

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KU ScholarWorks | The University of Kansas Pre-1923 Dissertations and Theses CollectionInstantaneous Chemical Reac-tions in Benzene and TolueneJune 7th, 1905by Herman Camp AllenThis work was digitized by the Scholarly Communications program staff in the KU Libraries’ Center for Digital Scholarship.http://kuscholarworks.ku.eduSubmitted to the Department of Chemistry of the University of Kansas in partial fulfillment of the requirements for the Degree of Master of ArtsMaster Thesis Chemistry Allen, H.C. 1905 "Instantaneous reactions (chemical) in benzene and toluene". I ! B f O H B M I O A L REACTIONS IN Bt«2F;»F! AND TQLUBMB, Presented to the faculty of the University of Kansas in partial fulfillment of the requirements for the Master of Arts decree by H*OvAlleiu 1906. INSTANTANEOUS OBBMIOAL RBAOTIOMS U BBNZBNE AND l'OLUBNB. Unt i l quits recently the study of ohemical reactions in solutions had been confined almost exclusively to those in which water was used as s solvent,and the phenomena exhibited have led to the advancement of many and varied theories by different men. Most conspicuous among these phenomena are the differences i n the conductivities of different solutions,and variations in the conductivity of the same solution with varying dilutionjand abnormal variations i n the vapor pressure with change of concentration as shown by the ab-normal depression of the freezing point,rise in the boiling point or change in the osmotic pressure;also the fact that the heat of n e u t r a l i -zation of the strong acids and strong bases i s a consfant in d i l u t e solutions. Shortly after the epoch making discoveries of Qalvani and Volta(l) Oavy(S) began his experiments with the e l e c t r i c p i l e which f i n a l l y re-sulted in the separation of the a l k a l i metals from their oxides.The result of his studies i s the electro-chemical theory that bears his name.This theory,however,never gained much prominence but soon gave place to the theory of Berzelius which differed from i t fundamentally i n that,while Davy believed that the atoms as such are e l e c t r i c a l l y zero,and become charged positive or negative by contact with other atoms,that take a charge of the opposite sign;Bsrzelius(3) claimed that every atom i s charged with both kinds of electricity.These exist upon the atom in polar arrangementand the e l e c t r i c a l and chemical g. | | | | 0 | g g n | ^ | | | t t ^ | | § | y » 3 2 6 - 8ilb.Ann.7,114,11801)j88,1,161(1808)* nature of the atom depends upon which kind of e l e c t r i c i t y i s present in excess. The theory of Srotthuss(l)to account for the electrolytic decomposition of water was very satisfactory for a time.Qrotthuss brought forward the view that.the molecules of an electrolyte arrange themselves polarly so as to form a chain:according to this hypothesis,which was beliefed for s some time,-and even yet finds a place in many text books,all the dissolved molecules in a solution take up such a position that their positively charged sides are towards the negative electrode,and the negativrly charged ones towards the positive electrode.During the electrolysis the positive atom next the negative electrode,and the negative one next the positive electrode,are separated.fhe negative atom of the f i r s t mole-cule now combines with the positive atom of the molecule next it,and this new molecule now turns round so as to take up a position similar to that of the original molecule* A step In the right direction was made by Williamson(8) who discarded these theories;eall«d s t a t i c a l because each atom was supposed to be at-tached to a particular atom of opposite sign in the solution;and believed "that i n an aggregate of the molecules of every MMMMMl-' ecmponnd, a oonsfi ant interchange between the elements contained in them i s taking place,B or that there i s movement among" the atoms.-Olausius,however,did not think i t necessary to go as far as Williamson but also recognised that the theory of Grotthuss was deficient.Accordingly he proposed what might be called a compromise,which supposed that under ordinary circumstances only a portion of the molecules of an electrolyte were broken down.Under the influence of an ele c t r i c current these part-1. • Annrde~0himI?iO ™ ' "™ "**""" 3. molecules w i l l be attracted to the electrode of opposite sign. Phis assumption of a partial breaking down of the molecules before the passage of a current accounted very satisfactory for the fact that a i very weak current could effect the decomposition of water containing a l i t t l e aoid.fhis w i l l be recognized at once as containing the fundamental proposition of the dissociation Theory1as proposed by Arrhanius in 1884* According to this theory the solute i s partially;pr i n dilute solut-ions entirely;broken down into a cation and an anion,carrying" a positive and a negative charge of electricity*Upon the passage of an electric c current through a solution containing these ions they w i l l move towards the electrode of opposite sign^fhe conductivity of the solution w i l l de-pend upon the extent to which this dissociation takes place,So far as the effect upon the vapor pressure of the solvent i s concerned,each of these 1 ions w i l l act the molecule and consequently w i l l produce ab-normal results when measured by either the depression of the freezing point,rise in the boiling point or variations in the osmotic pressure. fhe electrical conductivity and the variation in the vapor pressure furnish two distinct and independent methods for measuring" the degree of dissociation of a substance in solution.fhese have been determined for a great many substances and in nearly every case found to agree within the limits of the experimental error. Another fact,also,that haftdlong been observed but never before satisfact-o r i l y accounted for is that the heat of neutralization of a strong acid according to this theory,as In any case the only change taking place i s the combining" of the hydrogen.of the acid with the hydroxy! of the base fed form water while the remaining ions remain in their original condition* dilute solutions i s a constant.fhis i s necessary 4, It might also be addsd that this theory proposes that most chemical react ions,and especially instantaneous ones,are reactions between these ions. These facts along with many other ones,have led chemists in general to accept this explanation as the one that approaches nearest to the condition of a salt that i s in solution;and while i t i s recognized as being,not the widest g e n e r a l i s a t i o n ^ is at least believed to be an approximation. Kahlenberg has collected data and published papers at various times setting forth his reasons for not accenting' this theoryrand i t i s in a line suggested by one of these papers(l)that the present work has been dons. He chooses a hydraoarbon,benzene,as the solvent and finds that i t s e l e c t r i c a l conductivity i s practically nothing,when thoroughly dry# Then a solution of copper,nickel or cobalt oleate i s made and dried over sodium and the conductivity found to be no better than the benzene. These salts are chosen as they are practically the only salts of the heavy metals that are soluble in benzene.Next perfectly dry hydrachloric acid i s passed into the solution and immediately there i s formed a heavy,brown precipitate of the chloride of the metal. Here,then i s a case where we have no ionization as shown by the e l e c t r i c a l conductivity method but upon passing in the hy&rachloric acid a heavy precipitate i s formed^which shows that there must be ions present according to the same theory,and this i s the discrepancy shown XHxfikKXim$ftXX0Six*feE<2l^ i n the paper and which we w i l l attempt to account for.-lI5otii%pEy*r8K^ 5. Our chief work was done with and our conclusions drawn from substan-ces mentioned in the paper mentioned aboverthe solvents used being' benzine and toluene while the solutes were copper and cobalt oleate. ¥he salts wen's made substantially as described in the paper,the sodium salt being made f i r s t from solium hydroxid and then the sodium was replaced by the ©oppar or cobalt bn adding a slight excess of a solution of the sulfate of the heavy metal*fhe sodium hydroxid was made by allowing clean metallic sodium,placed under a bell-jar to react with water vapor from a dish of water placed under the same jar.fhe preoipi-tates;thick,tarry substances with the characteristic color of the copper and cobalt salts,werB then obtained by f i l t e r i n g off the liquids* They were then thoroughly washed and dried in an a i r bath heated to i©©*,t*Tomgn which air was drawn* ffceae salts were then dissolved in beonene and toluene aid fartbar dried by allowing to aland far several weeks ever metallia «a4ima«ffe observed,however,that the sodium soon became coated over with a very thin layer of fact was probably sodium oleate and would not not. upon the water even when i t was added to the solution*fhis protective layer was very thin and the sodium had the appearance of a freshly out metal-l i c surface#On account of the d i f f i c u l t y experienced in obtaining an-hydrous solutions In this way we tried another which seemed to give in better satisfaction and by means-of which the solutions could be thor-oughly dried in less than an hour* fhis method was to b o i l the solutions^nsing a reflux condenser,over metallic sodium pr potassium(fhe toluene over sodium and tjhe benzene solution over potassium)*The metals are fused at this temperature and by agitation new,bright metallic surfaces w i l l be exposed at a l l times* 6. Se sought, to obtain the same condition by using the f l u i d sodium-potas-sium alloy but found this less satisfactory. The solutions when dried i n th i s manner*become dark brown i n color and considerable quantities of a dark brown substance,which i s probably of the nature of a lake,are formed.This mixture was then'centrifuged* and within an hour after commencing to dry the solution was ready for* the conductivity determination and precipitation* Our hydrachloric acid was f i r s t generated as described fey Kahlenberg but later we found i t more convenient in and as reli a b l e to generate i t by means of an ordinary Kipp apparatus charged witii amionium chloric! and s u l f u r i c aeid*fhis showed a decided tendency to get through mr drying apparatus and retain traces of moisture and s© we passed i t through sulfuric acid and then through two drying towers i n se r i e s . These towers were 40 centimeters in height and about $ It diameter end were f i l l e d with alternate layers of pernio© stoae and phospaorms pentr oxid* The hydrogen used i n displacing the a i r was also generated in a Kipp and dried i n a t r a i n similar to the above,except, that only a single tower was used*This tower was connected to the last, one of the hydra-chloric acid tr a i n by means of the double arm of a two way stop oock while the single arm west to the c e l l used for measuring the conduct-i v i t y of the eolations,In a l l cases the hydrogen and hydrachlorio acid were passed slowly i n order to allow ample time i n the towers for thorough drying*** had some trouble at. f i r s t with a single tewor for drying the hydraehlorio acid and this lead to the tee of tee two towers* The c e l l was what p r a c t i c a l l y amounted to an Arrheaius resistance 7. o e l l with the electrodes less than a millimeter apart and with an area of 3,2 sq.cm.The lead wires were fused into the bottom of the c e l l . Sach time before using,the c e l l was cleaned with sulfuric acid and washed with fismnvi water,alcohol and ether*It. was. then placed i n posit* ion and strongly heated while dry hydrogen was passed through i t . I t contained a three hole,rubber stopper;one hole being used for introduc-ing the solution,another the hydrogen and 101 while the third was an exit and connected with a phosphorus pentoxid tube to kee.j the interior of the c e l l dry.fee exterior was kept dry by a casing,larger than the c e l l and containing PfOs and the lead wires were passed oat through the top and in s t a t e d by means of sulfur.The conductivity of this oell may be judged from the fact that hhe double deflection of a galvano-meter with a s e n s i b i l i t y of 300 megohms,with a difference of potential of 110 volts,only amounted to from 0*3 to 0*5. af a small(om) scale division when hhe o e l l contained a i r and would remain practically con-stant, for a period of twenty four hours* Our solutions were introduced by placing bee small Srlenmeyer i n which the drying and centrifuging had been done upon a two bole rubber stopperthat had been previously thoroughly cleaned and dried.One of tb.es holes connected to the hydrogen drying tower,while the other contained a glass tubethat dinned below the surface of the solution and connected , 'f with the cell.By turning on the hydrogen the solution could be forced into the c e l l without i t s being removed or any of the connections beiny broken.In fact nothing was removed from the measurement of the conduct-i v i t y of the empty c e l l t i l l the close of the experiment* The resistance of the galvanometer was 1300 ohms and i t . was con-nected in series with the c e l l and a reversing key and nryton shunt 8. No other resistance was in the circuit except the slight resistance of the lead wires and i t was subjected to the f u l l 110 volts*It was insalat ed from the possible leakage effects by being mounted upon a stand insulated by means of sulfur,which proved to be the best insulator for the purpose that we could f i n d . Invariably before measuring the conductivity ©f a solution the con-duetivity of the empty c e l l was taken and brought down by repeated heat-ing to a double deflection of less than a small scale division.Ho at-tempt was made to measure this conductivity exactly as i t was not con-sidered necessary. At the moment of introducing the solution with connections made we noticed a slight movement of the galvanometer which seen subsided and the conductivity returned to practically the conductivity of the empty celithough slightly better*fhinking to test whether the conduction was a well defined phenomena or only the result of accident we used a gal-vanometer about ten times as sensitive as the former and found that the solution showed decided conductivity#fith the dilute solutions with which we wwre working this would sometimes throw the galvanometer off the scale* fhe fact that the conductivity quickly diminished after introducing the solution led us to suspect polarination and we accordingly set i z about to measure it.For this purpose we used quite concentrated solution* to increase the effect and measured the polarisation by charging a condenser and then discharging through the more sensitive galvanometer. 'Uhe calibration was made by means of both standard Olark and Weston cells.When measured in this way a concentrated solution of copper oleafce in benzene gave a back S.M.F.of 1,9 volts*showing polarisation to that 9. extent.In the toluene solutions the polarisation was not so great but this may have been due to the fact that the solutions were not so con-centrated.In regard to the conductivity of these concentrated solutions they would frequently throw the mirror off the scale,even when shunted down t i l l only one thousandth of the current was passing through the instrument*This would diminish very appreciably after a few minutes and would usually remain on the scale with a l l the current acting*It addition to the back S.M.f.we believe that there i s a resistant f i l m formed that increases the resistance but have not had time to inv e s t i -gate as yet, Upon passing through the EG1 the conductivity was again increased which might be due to the breaking down of the film mentioned above; however at the moment, of precipitation the conductivity decreased and so markedly that the person at the telescope could t e l l to a nicety the moment the precipitate was formed by the movements of the galvano-meter* It mast be remarked that the formation of the precipitate;while quite rapid was by no means instantaneous,and i t eventually collected between the electrodes of the c e l l and increased the conductivity. The solutions of copper and cobalt oleate i n benzene and toluene are conductors of the seeond class because during conduction they ex-hibit the phenomena of polarisation*Sense i n these solutions ionization to an easily appreciable extent exists and the reaction between the HOI and the oleate i s exactly what would be expected from the stand-point of the 9ISS0CIA»IO» ¥1B0&T* Srenee, Kani *ne,f;i»§l 

Instantaneous Chemical Reactions in Benzene and Toluene

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Instantaneous Chemical Reactions in Benzene and Toluene

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