113 G e n e r a l a n d P h y s i c a l Chemistry. New Absorption Spectroscope. By &I. DO THIERRY (Compt. q*end., 101, 811--813).-An absorption spectroscope provided with a reflected scale and an eye-piece micrometer, and arranged so that columns of liquid varying in length from 0.1 m. to 10 m. can be examined, the source of illumination being an oxyhydrogen light. C. H. B. Electric Conductivity of Serpentine. By E. WIECHERT (A12n. Phys. Chem. [Z], 26, 336).-The conductivity of serpentine is very yariable ; the value of its specific resistance in terms of the mercury unit was found to lie between t,he limits of 20 and 30000 millions; its use as a perfect insulator is thus undesirable. Marble does not appear to conduct electricity under any observed conditions. V. H. V.Coefficient of Conductivity of Electrolytes in very dilute Solutions. By F. KOHLRACSCB (Ann; P h y . Chew. [2], 26, 161- 226).-A few years ago the author in conjunction with Nippolclt determined the coefficient of conductivity for several electrolytes, and showed that these could be arranged in groups, such as the halogen salts of the same metals, the potassium and auimonium salts, the chlorides of the alkaline earths, and the sulphates of magnesium, zinc, and copper. Further, in the case of neutral salts, the values of the temperature coefficients varied within very narrow limits with increase of dilution. As a general result, curves were drawn in which the proportions of salt in solution were taken as abscisse, and the coefficients of con- ductivity as ordinates ; the values of the former multiplied by the chemical equivalents are designated the spec?& molecular con- ductivities.The researches of Hittorf on the migration of the ions naturally cause an extension of the above researches in the case of very dilute solutions, as offering a possible means for the determination of the mean distance of the molecules. The method adopted was that of rapidly alternating currents, the results of former observers having shown thiit in working this rnethod, even when pushed to the most extreme limits, Ohm’s law is valid. The molecular proportions or values, m, of electrolytes in unit volume of solutions are understood to be the quantity in grams divided by the molecular weight ; such solutions were prepared in which the values for 7 t ~ were varied proportionally from 0.1 to 0.0001.The means adopted for preparing such solutions and their estimation, the detjr- mination of their conductivity, the correction for temperature, and other details are described at length in the paper. A series of tables are given of the coeficients of conductivity, KtlOlO, in terms of the mercury unit of such molecular solutions o€ VOL. L, i114 ABSTRACTS OF CHEMICAL PAFERS. various degrees of concentration of ammonium, sodium, li thium, barium, and zinc chlorides, barium, potassium, sodium, and silver nitrates, potassium, sodium, lithium, magnesium, zinc, and copper sulphates, sodium and potassium carbonates, of potassium iodide, chlorate, and acetate, and of nitric, hydrochloric, and sulphuric acids.Conductivity of Salts.-These determinations show that the con- ductivity atl first varies directly as the molecular proportion, but in the more dilute solutions the value for this ratio gradually diminishes ; the former divided by the -latter, kfm, is the specific molecular con- ductlziit?y (comp. supra). The values for k / m can best be interpreted by considering them as proportional to the relative velocity of the ions under the influence of a constant electromotive force. If then the values for 1O87c/rn be multiplied by 0*00011, one obtains the velocity in mm./seconds with which the ions pass one another, under the influence of the force of one volt acting through 1 mm. Unequal values are thus obtained, as shown by the following table :- Kations. I(. PTH,.Na. Li. Ag. H. +Bn. +ME. +Zn. ?u = l@*k/m x 0*00011 52 30 32 24 42 272 30 26 '20 w = lO*X./nz x 0.00011 84 55 48 42 26 143 It is thus seen that potassium and ammonium, magnesium and zinc, and in dilute solutions Sod, I, C1, and NO3, can be classified together in separate groups, a, result in accordance with the experi- ments of Lenz. Further, it is shown that the water of crystallisation has no influence on the conductivity of the salts. Ceretain experiments of Faraday and Gmelin are also repeated, ~ihich tend to show that in the case of very dilute solutions not only the dissolved electrolyte, but also, under certain conditions, the water itself is decomposed. Thus if a trace of ammonium carbonate be added to solutions of magnesium and copper sulphates, a precipitation of the hydroxide of the metal appears generally in a dendritic form.Bouty's law of equivalents (Thbis, Paris, 1885) is examined and not found to be generally valid. The temperature coefficients of solutions containing m = 0.01 of the various salts examined were found to be approximately equal. Conductivity qf Alkalis and Acids.--The coefficient of these Fiibstamces relatively to dilution at first increases, reaches a maximum, :.nd then decreases ; the maximum occurs with solutions in which '1t1 5= 0-OM. The following results are also mentioned : (1) the specific conduc- tivities of potassium and sodium hgroxides are approximately equal, a s also those of the halogen and nitric acid ; (2) solutions of ammonia and of phosphoric and acetic acids, are exceedingly bad conductors ; (3) the curve representing the conductivity of sulphuric acid shows minimum points of inflexion corresponding with the formation of the nionohydrate H2S04,H,0, the pure acid H2S04, and the anhF-dride respectively.The temperature coefficients of alkalis and acids, with the exception of sulphuric acid, are also approximately equal. Anions. C1. I. NO,. C103. C,H,O,. OH.GENERAL AND PHYSICAL CHEMISTRY. 115 Researches are also promised on the application of the determina- tions of conductivity for ascertaining the interaction of acids and bases when in the same solution. V. H. V. Electrical Conductivity of Mixtures of Ethyl Alcohol and Ether. By E. W. R. PFEIFFER (Ann. Phys. Chem. [2], 26,226-239). I n Continuation of the author’s researches on the conductivity of organic liquids (Abstr., 1885,1029), an account is given of determina- tions of the specific Conductivity of mixtures of alcohol and ether as functions (1) of the percentage proportion of the latter, the tempe- rature being constant ; and (2) of the temperature, the mixtures being of identical composition.Firstly. The conductivity of such a mixture decreases a t first regularly with increase of proportion of ether, until the liquid con- tains 75 per cent. ; a t this point the curve representing conductivity in terms of percentage of ether shows a point of inflexion, and thence approaches more gradually to the axis of the abscissze, until with pure ether the conductivity cannot be measured. It was observed inci- dentally that the conductivity of such mixtures, kept a t constant temperature, slowly decreases from the moment of mixing until a minimum point is reached after a variable interval of time ; from this point, the conductivity again increases. As it is improbable that the mere passage of the current should effect the conductivity, this phe- nomenon may be due to t(he chemical action between inevitable impurities in the liquids or between the liquids themselves.Secondly. The temperature coefficient is negative for mixtures con- taining less than 24 to 29 per cent. ether, a t which point it becomes zero ; thence it increases, reaches a maximum with 35 per cent., and then again decreases. Thus both pure alcohol and ether, as also mixtures of them in certain proportions, resemble metallic conductors as regards the negative value of their temperature coefficient.By A. XENARD (Cowpi. rend., 101, 747 -7‘49) .-From the results of experiments with aqueous solutions of various salts containing from 0.0001 to 0.1024 gram-equivalent of the metals in 100 grams of solution, the author concludes (1) that iE the solution be sufficiently dilute the quantity of metal precipitated is proportional to the concentration of the solution ; (2) that if the same current is passed through several solutions, the quantities of the different metals precipitated are in the ratios of their equivalents ; (3) that, according to Faraday’s law, the quantity of metal precipi- tated being proportional to the intensity of the current, the conduc- tivity of all solutions containing equivalent proportions of the different metals is the same, as Bouty has shown by direct experi- ment.C. H. B. V. H. V. Electrolysis of Salts. New Method of Determining the Heat of Combustion of Organic Substances. By D. DIACONOFF ( J . RUSS. Chem. XOC., 1885, 283 -284) .-The anthor burns the compound under investigation in admixture with finely powdered asbestos and glycerol ; the former i 2116 ABSTRACTS OF CHEMICAL PAPKRS. divides the particles of the difficultly combustible substance, and secures its entire combustion, the latter maintains the temperature necessary for combustion. A. T. Relations between the Heat of Formation of Salts and the Initial Rate of their Formation. By A. POTILITZIN (Rer., 18, 1522--1527).-When silver chloride is shaken in the dark with equally concentrated solutions of metallic bromides for three minutes and then allowed to rest for 25 minutes, varying percentages of silver bromide are obtained according to the metallic bromide used.T h e n these percentages are divided by the heat of formation of silver bromide from the metallic bromide, a constant number is obtained; in this case the number is 11.17. Similar results are obtained if instead of silver chloride and a bromide, equivalent quantities of AgN03 + RCl + RBr are employed. Comparisons were also made of the percentages of carbonates formed by the action of alkaline carbonates on the chlorides of the alkaline earths and of the heat of formation. I n this case also a con- stant, namely 1 4 . 1 , was obtained by dividing the percentage by the heat of formation.I n these experiments, dilute solutions must be used ; further, the initial rates of formation of different salts can only be compared in the case of reactions which take place under quite similar circum- stances. N. H. M. Air or Hydrogen Thermometer for Low Temperatures. By J. J. COLEMAN (J. Soc. Chem. Ind., 4, 43).-This instrument is a constant pressure thermometer, and has been specia,lly constructed for taking low temperatures, say to 300" below zero Fahrenheit. New Form of Gas Thermometer. By G. BEILBY ( J . XOC. Chem. Ind., 4, 40).-The author has attempted the construction of a com- pact thermometer on the principle of measuring a t known and con- stant temperature and pressure the gas expelled from a bulb or vessel of unknown temperature. D.B. D. B. Source of Error in Vapour-density Determinations. By W. ALEXEEFF ( B e y . 18, 2898-2906) .-In order to explain the discordant results obtained by Meyer and Pond (Abstr., 1885, 1033) on the one hand, and by Menschutkin and Konowalow (Abstr., 1884,1119) on the other hand, in experiment's on the dissociation of tertiary amyJ acetate and chloride induced by glass (Abstr., 1884, 1119), the author men- tions the fact that the glass used in Russia is much more readily attacked by acids and other reagents than German glass. Experiments are quoted with propyl bromide which show that in a Meyer's appa- ratus no dissociation takes place a t the boiling point of nitrobenzene, whereas 40 per cent. is dissociated a t 200". This latter result can be interpreted by the removal of the traces of hydrobromic acid by the vapour of water produced by a chemical action on the glass.If this interpretation be correct, the amount of dissociation will be greater, the greater the ratio of the glass surface to vapour present, a resultGEXERAL AND PHYSICAL CHEMISTRY. 117 Of temperature. in accordance wit,h the most recent experiments of Menschntkin and Konowalow. V. H. V. tion. Of pressure. Dissociation of the Hydrate of Hydrogen Bromide. By H. W. B. ROOZEBOOM (Rec. Trav. Chim., 4, 108--124).-The curve of tensions of the hydrate of hydrogen bromide between the temperatures of - 11.3" and - 15.6' recurves in a negative direction, there being three different tensions of dissociation for a given temperature between these points.At the lower tension a t 11*3", the aqueous solution of the hydrate surrounding the solid reaches such a concentration that it has a composition identical with that of the solid hydrate itself. Van der Waals has already pointed out that when this takes place a t a lower temperature than that at which the acid or chlorous product of dissociation is given off in the liquid form, the curve of dissociation tensions will take a negative direction limited by a point whose position depends on the heat of formation of the compound in question ; the curve then once more assumes a positive direction, and the tension rises with the temperature in the normal manner. The hydrate of hydrogen chloride (Eec. Trtsv. Chim., 3, 94) shows a similar phenomenon, but the length of the recurved portion is much shorter.A. P. - 9.5" to - 2.6" - 2.6 ), + 12.1 + 16.2 ), + 17'1 Dissociation of the Hydrates of Sulphurous Anhydride, Chlorine, and Bromine. By H. W. B. ROOZEBOOM ( B e c . Trav. Chim., 4, 65--73).-1n Continuation of his researches on this subject ( R e c . T ~ a v . Chim., 3, 28-104) the author finds that the curves representing the tensions of dissociation of these compounds a t diiTerent temperatures, are each broken into three segmental curves having different directions, the points of intersection being coincident with the temperatures at which a change ,of state takes place in one of the products of dissociation. The main detai-1s are given in the following tables :- 150 mm. to 211 mm. 211 mm. ,, 177 cm. H& liquid and SO2 ,, 177 cm.,, 250 atm. H20 ), and SO2 liquid H,O solid and SO, gaseous I. SO, + 7H,O. Points of intersecfion at - 2 *ti" and +- 12 *lo.118 Of temperature. ABSTRACTS OF CHEMICAL PAPERS. Of pressure. IT. C1, + 8H,O. Intervals - loo to - 0.24' - 0.24' ,, + 28.T + 28-7" ,, - 156 mm. to 248 mm. 248 mm. to about 6 atm. 6 atm. to - Products of dissocia- tion. H,O solid and C1, gaseous H,O liquid and C1, ,, H,O ,, and C1, liquid Points of intersection a t - 0.24' and + 28.7". 111. Br, + 1OH,O. Of temperature. ~ Intervals Produats of dissocia- tion. Of pressure. - 10' to - 0.30 - 0.3' ,, + 6 . 2 f 6'2" ,, - -I------ -- 25 mm. to 43 mm. 43mm. ,, 93mm. 93mm. ,, - H,O solid and Br, gaseous H,O liquid and Br2 ,, H,O ,, and Br2 liquid Points of inteasection at - 0.3" and + 6.2".A. P. Air-pump Regulator. By N. v. KLOBUKOW (Zeit. anal. Chem., 24, 399-402).-A. simple apparatus by means of which the reduced pressure obtained by means of a water jet air-pump may be rendered constant within 1.0 cm. at whatever pressure required, and however the rate of fiow Q€ the water may vary. A. P.113G e n e r a l a n d P h y s i c a l Chemistry.New Absorption Spectroscope. By &I. DO THIERRY (Compt.q*end., 101, 811--813).-An absorption spectroscope provided with areflected scale and an eye-piece micrometer, and arranged so thatcolumns of liquid varying in length from 0.1 m. to 10 m. can beexamined, the source of illumination being an oxyhydrogen light.C. H. B.Electric Conductivity of Serpentine. By E. WIECHERT (A12n.Phys.Chem. [Z], 26, 336).-The conductivity of serpentine is veryyariable ; the value of its specific resistance in terms of the mercuryunit was found to lie between t,he limits of 20 and 30000 millions;its use as a perfect insulator is thus undesirable.Marble does not appear to conduct electricity under any observedconditions. V. H. V.Coefficient of Conductivity of Electrolytes in very diluteSolutions. By F. KOHLRACSCB (Ann; P h y . Chew. [2], 26, 161-226).-A few years ago the author in conjunction with Nippolcltdetermined the coefficient of conductivity for several electrolytes, andshowed that these could be arranged in groups, such as the halogensalts of the same metals, the potassium and auimonium salts, thechlorides of the alkaline earths, and the sulphates of magnesium,zinc, and copper. Further, in the case of neutral salts, the values ofthe temperature coefficients varied within very narrow limits withincrease of dilution.As a general result, curves were drawn in which the proportions ofsalt in solution were taken as abscisse, and the coefficients of con-ductivity as ordinates ; the values of the former multiplied by thechemical equivalents are designated the spec?& molecular con-ductivities.The researches of Hittorf on the migration of the ions naturallycause an extension of the above researches in the case of very dilutesolutions, as offering a possible means for the determination of themean distance of the molecules.The method adopted was that of rapidly alternating currents, theresults of former observers having shown thiit in working this rnethod,even when pushed to the most extreme limits, Ohm’s law is valid.The molecular proportions or values, m, of electrolytes in unit volumeof solutions are understood to be the quantity in grams divided by themolecular weight ; such solutions were prepared in which the valuesfor 7 t ~ were varied proportionally from 0.1 to 0.0001.The meansadopted for preparing such solutions and their estimation, the detjr-mination of their conductivity, the correction for temperature, andother details are described at length in the paper.A series of tables are given of the coeficients of conductivity,KtlOlO, in terms of the mercury unit of such molecular solutions o€VOL.L, 114 ABSTRACTS OF CHEMICAL PAFERS.various degrees of concentration of ammonium, sodium, li thium, barium,and zinc chlorides, barium, potassium, sodium, and silver nitrates,potassium, sodium, lithium, magnesium, zinc, and copper sulphates,sodium and potassium carbonates, of potassium iodide, chlorate, andacetate, and of nitric, hydrochloric, and sulphuric acids.Conductivity of Salts.-These determinations show that the con-ductivity atl first varies directly as the molecular proportion, but inthe more dilute solutions the value for this ratio gradually diminishes ;the former divided by the -latter, kfm, is the specific molecular con-ductlziit?y (comp. supra). The values for k / m can best be interpretedby considering them as proportional to the relative velocity of theions under the influence of a constant electromotive force.If thenthe values for 1O87c/rn be multiplied by 0*00011, one obtains the velocityin mm./seconds with which the ions pass one another, under theinfluence of the force of one volt acting through 1 mm. Unequalvalues are thus obtained, as shown by the following table :-Kations. I(. PTH,. Na. Li. Ag. H. +Bn. +ME. +Zn.?u = l@*k/m x 0*00011 52 30 32 24 42 272 30 26 '20w = lO*X./nz x 0.00011 84 55 48 42 26 143It is thus seen that potassium and ammonium, magnesium andzinc, and in dilute solutions Sod, I, C1, and NO3, can be classifiedtogether in separate groups, a, result in accordance with the experi-ments of Lenz.Further, it is shown that the water of crystallisation has no influenceon the conductivity of the salts.Ceretain experiments of Faraday and Gmelin are also repeated,~ihich tend to show that in the case of very dilute solutions not onlythe dissolved electrolyte, but also, under certain conditions, the wateritself is decomposed.Thus if a trace of ammonium carbonate beadded to solutions of magnesium and copper sulphates, a precipitationof the hydroxide of the metal appears generally in a dendritic form.Bouty's law of equivalents (Thbis, Paris, 1885) is examined andnot found to be generally valid.The temperature coefficients of solutions containing m = 0.01 of thevarious salts examined were found to be approximately equal.Conductivity qf Alkalis and Acids.--The coefficient of theseFiibstamces relatively to dilution at first increases, reaches a maximum,:.nd then decreases ; the maximum occurs with solutions in which'1t1 5= 0-OM.The following results are also mentioned : (1) the specific conduc-tivities of potassium and sodium hgroxides are approximately equal,a s also those of the halogen and nitric acid ; (2) solutions of ammoniaand of phosphoric and acetic acids, are exceedingly bad conductors ;(3) the curve representing the conductivity of sulphuric acid showsminimum points of inflexion corresponding with the formation of thenionohydrate H2S04,H,0, the pure acid H2S04, and the anhF-driderespectively. The temperature coefficients of alkalis and acids, withthe exception of sulphuric acid, are also approximately equal.Anions.C1. I. NO,. C103. C,H,O,. OHGENERAL AND PHYSICAL CHEMISTRY. 115Researches are also promised on the application of the determina-tions of conductivity for ascertaining the interaction of acids andbases when in the same solution. V. H. V.Electrical Conductivity of Mixtures of Ethyl Alcohol andEther. By E. W. R. PFEIFFER (Ann. Phys. Chem. [2], 26,226-239).I n Continuation of the author’s researches on the conductivity oforganic liquids (Abstr., 1885,1029), an account is given of determina-tions of the specific Conductivity of mixtures of alcohol and ether asfunctions (1) of the percentage proportion of the latter, the tempe-rature being constant ; and (2) of the temperature, the mixtures beingof identical composition.Firstly.The conductivity of such a mixture decreases a t firstregularly with increase of proportion of ether, until the liquid con-tains 75 per cent. ; a t this point the curve representing conductivityin terms of percentage of ether shows a point of inflexion, and thenceapproaches more gradually to the axis of the abscissze, until with pureether the conductivity cannot be measured. It was observed inci-dentally that the conductivity of such mixtures, kept a t constanttemperature, slowly decreases from the moment of mixing until aminimum point is reached after a variable interval of time ; from thispoint, the conductivity again increases. As it is improbable that themere passage of the current should effect the conductivity, this phe-nomenon may be due to t(he chemical action between inevitableimpurities in the liquids or between the liquids themselves.Secondly. The temperature coefficient is negative for mixtures con-taining less than 24 to 29 per cent.ether, a t which point it becomeszero ; thence it increases, reaches a maximum with 35 per cent., andthen again decreases.Thus both pure alcohol and ether, as also mixtures of them incertain proportions, resemble metallic conductors as regards thenegative value of their temperature coefficient.By A. XENARD (Cowpi. rend., 101, 747-7‘49) .-From the results of experiments with aqueous solutions ofvarious salts containing from 0.0001 to 0.1024 gram-equivalent of themetals in 100 grams of solution, the author concludes (1) that iE thesolution be sufficiently dilute the quantity of metal precipitated isproportional to the concentration of the solution ; (2) that if the samecurrent is passed through several solutions, the quantities of thedifferent metals precipitated are in the ratios of their equivalents ;(3) that, according to Faraday’s law, the quantity of metal precipi-tated being proportional to the intensity of the current, the conduc-tivity of all solutions containing equivalent proportions of thedifferent metals is the same, as Bouty has shown by direct experi-ment.C. H. B.V. H. V.Electrolysis of Salts.New Method of Determining the Heat of Combustion ofOrganic Substances. By D. DIACONOFF ( J . RUSS. Chem. XOC., 1885,283 -284) .-The anthor burns the compound under investigationin admixture with finely powdered asbestos and glycerol ; the formeri 116 ABSTRACTS OF CHEMICAL PAPKRS.divides the particles of the difficultly combustible substance, andsecures its entire combustion, the latter maintains the temperaturenecessary for combustion. A.T.Relations between the Heat of Formation of Salts and theInitial Rate of their Formation. By A. POTILITZIN (Rer., 18,1522--1527).-When silver chloride is shaken in the dark withequally concentrated solutions of metallic bromides for three minutesand then allowed to rest for 25 minutes, varying percentagesof silver bromide are obtained according to the metallic bromideused. T h e n these percentages are divided by the heat of formationof silver bromide from the metallic bromide, a constant number isobtained; in this case the number is 11.17.Similar results areobtained if instead of silver chloride and a bromide, equivalentquantities of AgN03 + RCl + RBr are employed.Comparisons were also made of the percentages of carbonatesformed by the action of alkaline carbonates on the chlorides of thealkaline earths and of the heat of formation. I n this case also a con-stant, namely 1 4 . 1 , was obtained by dividing the percentage by theheat of formation.I n these experiments, dilute solutions must be used ; further, theinitial rates of formation of different salts can only be compared inthe case of reactions which take place under quite similar circum-stances. N. H. M.Air or Hydrogen Thermometer for Low Temperatures.ByJ. J. COLEMAN (J. Soc. Chem. Ind., 4, 43).-This instrument is aconstant pressure thermometer, and has been specia,lly constructedfor taking low temperatures, say to 300" below zero Fahrenheit.New Form of Gas Thermometer. By G. BEILBY ( J . XOC. Chem.Ind., 4, 40).-The author has attempted the construction of a com-pact thermometer on the principle of measuring a t known and con-stant temperature and pressure the gas expelled from a bulb or vesselof unknown temperature. D. B.D. B.Source of Error in Vapour-density Determinations. By W.ALEXEEFF ( B e y . 18, 2898-2906) .-In order to explain the discordantresults obtained by Meyer and Pond (Abstr., 1885, 1033) on the onehand, and by Menschutkin and Konowalow (Abstr., 1884,1119) on theother hand, in experiment's on the dissociation of tertiary amyJ acetateand chloride induced by glass (Abstr., 1884, 1119), the author men-tions the fact that the glass used in Russia is much more readilyattacked by acids and other reagents than German glass.Experimentsare quoted with propyl bromide which show that in a Meyer's appa-ratus no dissociation takes place a t the boiling point of nitrobenzene,whereas 40 per cent. is dissociated a t 200". This latter result can beinterpreted by the removal of the traces of hydrobromic acid by thevapour of water produced by a chemical action on the glass. If thisinterpretation be correct, the amount of dissociation will be greater,the greater the ratio of the glass surface to vapour present, a resulGEXERAL AND PHYSICAL CHEMISTRY.117Of temperature.in accordance wit,h the most recent experiments of Menschntkin andKonowalow. V. H. V.tion.Of pressure.Dissociation of the Hydrate of Hydrogen Bromide. By H.W. B. ROOZEBOOM (Rec. Trav. Chim., 4, 108--124).-The curve oftensions of the hydrate of hydrogen bromide between the temperaturesof - 11.3" and - 15.6' recurves in a negative direction, there beingthree different tensions of dissociation for a given temperature betweenthese points. At the lower tension a t 11*3", the aqueous solution ofthe hydrate surrounding the solid reaches such a concentration thatit has a composition identical with that of the solid hydrate itself.Van der Waals has already pointed out that when this takes place a ta lower temperature than that at which the acid or chlorous productof dissociation is given off in the liquid form, the curve of dissociationtensions will take a negative direction limited by a point whoseposition depends on the heat of formation of the compound inquestion ; the curve then once more assumes a positive direction, andthe tension rises with the temperature in the normal manner.Thehydrate of hydrogen chloride (Eec. Trtsv. Chim., 3, 94) shows asimilar phenomenon, but the length of the recurved portion is muchshorter. A. P.- 9.5" to - 2.6"- 2.6 ), + 12.1 + 16.2 ), + 17'1Dissociation of the Hydrates of Sulphurous Anhydride,Chlorine, and Bromine. By H. W. B. ROOZEBOOM ( B e c . Trav.Chim., 4, 65--73).-1n Continuation of his researches on this subject( R e c . T ~ a v . Chim., 3, 28-104) the author finds that the curvesrepresenting the tensions of dissociation of these compounds a tdiiTerent temperatures, are each broken into three segmental curveshaving different directions, the points of intersection being coincidentwith the temperatures at which a change ,of state takes place in oneof the products of dissociation. The main detai-1s are given in thefollowing tables :-150 mm. to 211 mm.211 mm. ,, 177 cm. H& liquid and SO2 ,,177 cm. ,, 250 atm. H20 ), and SO2 liquidH,O solid and SO, gaseousI. SO, + 7H,O.Points of intersecfion at - 2 *ti" and +- 12 *lo118Of temperature.ABSTRACTS OF CHEMICAL PAPERS.Of pressure.IT. C1, + 8H,O.Intervals- loo to - 0.24'- 0.24' ,, + 28.T + 28-7" ,, -156 mm. to 248 mm.248 mm. to about 6 atm.6 atm. to -Products of dissocia-tion.H,O solid and C1, gaseousH,O liquid and C1, ,,H,O ,, and C1, liquidPoints of intersection a t - 0.24' and + 28.7".111. Br, + 1OH,O.Of temperature.~IntervalsProduats of dissocia-tion.Of pressure.- 10' to - 0.30 - 0.3' ,, + 6 . 2f 6'2" ,, --I------ --25 mm. to 43 mm.43mm. ,, 93mm.93mm. ,, -H,O solid and Br, gaseousH,O liquid and Br2 ,,H,O ,, and Br2 liquidPoints of inteasection at - 0.3" and + 6.2".A. P.Air-pump Regulator. By N. v. KLOBUKOW (Zeit. anal. Chem.,24, 399-402).-A. simple apparatus by means of which the reducedpressure obtained by means of a water jet air-pump may be renderedconstant within 1.0 cm. at whatever pressure required, and howeverthe rate of fiow Q€ the water may vary. A. P