SOLUBILITY, ELECTROLYTIC CONDUCTIVITY A N D CHEMICAL ACTION I N LIQUiD HYDROCYANIC ACID
BY LOUIS KAHLENBERG AND HERMAN SCHLUNDT
T h e properties of solutions in which liquid hydrocyanic acid is the solvent are of importance in investigating the general problem of nature of solutions. Special interest attaches to the electrical conductivity of solutions in liquid hydrocyanic acid because of the high dielectric constant of this solvent.’ Some time ago we made preliminary tests2 of the electrical conductivity of solutions in liquid hydrocyanic acid ; but before we could collect a sufficient number of quantitative measurements to warrant a publication of them, M. Centnerszwer,3 a t the request of P. Walden, measured the electrical conductivity of two substances, K I and S(CH3)31in liquid HCN.4 These solutions H. Schlundt, Jour. Phys. Chem. 5, 191 ( I ~ O I ) found , the dielectric con. stant of liquid HCN to be 95. Jour. Phys. Chem. 5, 162 and 384 (1901). Zeit. phys. Chem. 39, 220 (1901). These determinations of M Centnerszwer were clearly made after the work on the same subject had been begun in this laboratory, and after the article in Jour. Phys. Chem. 5, 759 (1901)had appeared ; for in speaking of the desirability of measuring the conductivity of solutions in liquid HCh-, M. Centnerszwer (1. c.) mentions Jour. Phys. Chem. 5, 159 (1901)and says :- ‘ i Es schien dies um so mehr lohnenswert, als die vor kurzem veroffentlichten Versuche von Schlundt diesem Korper eine Dielektrizitatskonstante von 95 zuschreiben -.” We therefore wish to call attention to the fact on p. 162, Vol. 5, Jour. Phys. Chem., is the statement : I ‘ an investigation of the conductivity and other properties of salts dissolved in hydrocyanic acid is now i n progress in this laboratory,” and that the priority claim with which Centnerszwer closes his article : ‘‘ Da inzwischen die Ausfiihrung ahnlicher Messungen von anderer Seite (1,. Kahlenberg, Jour Phys. Chem. 5 , 384 (1901)) angekundigt wurde, so hielt ich es fur angemessen, das vorlaufig von mir i n dieser Frage gesammelte Material hier mitzuteilen ” is not justifiable, since announcement of the progress of our measurements was made in the earlier article, Jour. Phys. Chem. 5, 162 (1901). It is of course immaterial for the progress of the science as to who makes the investigations ; but in justice t o
448
L. Kahlenberg and H. Schlundt
he found to be better conductors than the corresponding aqueous solutions. * T h e hydrocyanic acid used was prepared by gradually adding a strong solution of Kahlbaum's best potassium cyanide to a solution of pure sulphuric acid of 1.25 sp gr, which was contained in a retort connected with a reflux condenser, whose temperature was kept at 30' C. T h e gas was dried by passing it through a series of three large U-tubes filled with fused calcium chloride, and finally through two such tubes containing dry pumice covered with phosphorus pentoxide. These drying tubes were also kept at 30" C. T h e thoroughly dried gas was then conducted into two glass bottles immersed i n an ice-bath. T h e liquid obtained by thus condensing the gas was colorless and left no residue upon evaporation. Its specific electrical conductivity varied somewhat in the case of different samples that were prepared. T h e results of these conductivity measurements are given in the tables below. In this connection we desire simply to emphasize that the sample of lowest conducting power had a specific condiictivity of 0,473 X 10-5 reciprocal ohms at 0'. This figure is lower than the one (0.496 X 10-5 reciprocal Siemen's units) that M. Centnerszwer' obtained in the
__ ourselves, we feel that attention should be called to the facts here presented. I t should further be stated, that work on the so-called dissociative power of solvents was published from this laboratory in the Jour. Phys. Cliem. 3, 12 ( ~ S g g ) ,and that the research included a number of inorganic solvents (notably PCl,, ASCI,, SnC1,) as well as a large number of organic solvents. In that article it was made evident that it was desirable to subject to further investigation the dielectric constants of many solvents. This work was consequently done by H. Schlundt, Jour. Phys. Chem. 5, pp. 157 and 503 (1901). After the publication of the first article on dissociative power of solvents from this laboratory in 1899, Walden took up his admirable, extensive researches on the dissociative power of inorganic solvents. H e did not measure the dielectric constantsof these solvents, nor did he even announce his attention to make such measurements. I n view of this and the additional fact that work on the dissociative power of solvents, both inorganic and organic, was done here before Walden began his researches on inorganic solvents, the insinuation of the latter that the studies of H. Schlundt on the dielectric constants of (both organic and inorganic) solvents constitute a continuation of his ( Walden's) work is clearly unjust. 1. c.
Colza'uclivity in Liquid Hydrocyanic .4cd
449
case of his most carefully prepared sample. T h e resistance cell consisted of a graduated and calibrated tube of about 2 0 cc capacity, closed at one end into which the electrodes were fused. T h e latter consisted of two rectangular pieces of heavy platinum foil to which were welded short pieces of platinum rod, the joints being further carefully secured by means of soldering with gold. T h e electrodes were placed in a vertical position in the tube. T o the end of the platinum rods, which projected slightly beyond the glass tube, copper wires about I mm in diameter were carefully soldered. These were covered with an excellent rubber insulation, and the soldered joints and the projecting platinum rods were carefully coated with wax. T h e insulation thus secured was tested and was found to be entirely satisfactory. T h e copper wires were conducted upward parallel to the glass tube of the cell, being held close to the outer wall of the latter by means of small rubber bands. These copper wires were long enough to allow the cell to be immersed in an ice-bath and at the same time to be connected conveniently with the rheostat and the bridge of the Wheatstone combination. T h e electrodes were coated with platinum black. T h e volume of the liquid in the tube could be read to 0.02 cc. T h e so-called resistance capacity of the cell was determined by means of a ;IZ/SO KC1 solution (whose specific conductivity was taken to be 0.002765 in reciprocal ohms at 25" C) and was found to be 0.4264. T h e upper end of the resistance cell was securely closed by means of an excellent rubber stopper. All the conductivity measurements were made at 0" C by means of the well-known method devised by Kohlrausch. In making a series of determinations, the liquid hydrocyanic acid was first run into the cell. And after the conductivity of the pure solvent had been determined, very carefully weighed quantities of the solute were successively introduced into the cell, the volume of the liquid and the conductivity being noted in each case. T h e substances employed were all of a high degree of purity,
450
L. KahZenberg ana? H. SchZacndt
and special care was taken to guard against the presence of moisture. Besides the quantitative measurements of electrical conductivity of solutions in liquid hydrocyanic acid given in Tables I to 24 below, a large number of qualitative solubility and conductivity tests were made, the results of which will now be presented. In this work it was sought to select representative substances of various kinds. T h e following substances are readily soluble in liquid hydrocyanic acid, but the resulting solutions are non-electrolytes, their conductivity being no greater than that of the solvent itself, and commonly less : Iodine, water, methyl alcohol, ethyl alcohol, glycerine, ethyl ether, phenol, picric acid, resorcine, menthol, acetic aldehyde, chloral, benzaldehyde, acetone, benzophenone, ethyl iodide, chloroform, propyl nitrate, aceto-acetic ester, benzene, benzil, urea, urethane, aniline, $-toluidine, xylidine, camphor, borneol, ethylene cyanide, a-naphthonitrile, @-naphthonitrile, amyl sulphydrate, benzoic acid, cinnamic acid, tin tetrachloride, tin tetrabromide, tin tetraiodide, sulphur monochloride, nicotine, theobromine, caffeine, papaverine, narcotine, cyanine, Hoffmann’s violet. T h e following are soluble in liquid hydrocyanic acid, but the resulting solutions are very poor1 conductors of ‘electricity : Acetic acid, cyanacetic acid, trichloracetic acid, trichlorlactic acid, crotonic acid, o-nitrobenzoic acid, amidobenzoic acid, pyridine, quinoline, phenylhydrazine, benzaniide, acetanilide, diphenyl amine, aconitine, coniine, dLlphine,arsenic trichloride, antimony trichloride. T h e following are soluble in liquid hydrocyanic acid and yield solutions of fair conducting power : Bismuth trichloride, silver nitrate,* strychnine, morphine, brucine, atropine, cocaine, 1 A fair idea of the extent of the conduction of these substances may be formed from the quantitative measurements that were made in a number of cases -see tables below. This salt is only sparingly soluble iii liquid HCN.
Coizductivity in Liquid Nydvocyaizic Acid
451
veratrine, acetyl chloride, phosphorus oxychloride, thionyl chloride,' sullphuryl chloride.' T h e following dissolve in liquid hydrocyanic acid and the resulting solutions are good electrolytes : Potassium iodide, potassium sulphocyanate, potassium permanganate, potassium cyanate, platinum potassium cyanide, ferric chloride, antimony pentachloride, hydrochloric acid, sulphur trioxide, sulphuric amyl amine, and NH(C,Hrl)CS.SNHj(C5HJz acid (H2S04), T h e following substances are sparingly soluble in liquid hydrocyanic acid, thesolubility being detected in the case of the salts by the increase of the electrical coiiductivity of the saturated solution above that of the pure solvent : Sodium chloride, potassium chloride, ammonium chloride, sodium bromide, potassium nitrate, sodium nitrate, potassium sulphate, potassium chromate, borax glass, sodium oleate, potassium platinic chloride, potassium phthalimide, cob.tltous chloride, cadmium iodide, mercuric chloride, mercuric bromide, cupric arsenite, cupric arsenate, silver sulphate, silver cyanide, silver cyanate, arsenic triiodide, tartaric acid, camphoric acid, boric acid, biuret, thiourea, quinine, sulphate, brucine chloride. T h e substances that were found to be insoluble in liquid hydrocyanic acid are : Calcium chloride, bariuni chloride, calcium nitrate, strontium nitrate, barium nitrate, lead fluoride, lead bromide, lead iodide, lead chromate, mercurous chloride, mercuric iodide, mercuric oxide, cadmium nitrate, cadmium sulphate, cupric sulphate, cuprous cyanide, cupric oleate, aluminum chloride, stannous chloride, silver chloride, silver cyanide, silver cyanacetate, chromium trioxide, phosphorus pentoxide, iodic acid, oxalic acid anhydride, phthalic acid anhydride, petroleum ether, paraffine, naphthalene, carbon djsulphfde, iodoform, oleic acid, palmitic acid, stearic acid, cane-sugar, levulose, erythrite, asparagine, phenol-phthaleine, fluoresceine, naphthol green, alloxan, alloxantine.
.
The solutions of these substances showed an increase of conductivity with lapse of time. Furthermore, the solutes may have contained traces of moisture in these two cases. Prepared by treating carbon disulphide with amyl amine.
b
In the following tables giving the results of quantitative measurements of electrical conductivity of solutions in liquid hydrocyanic acid, z, represents the volume in liters in which one gram-molecule of solute is contained, and A the molecular conductivity of the solutions in reciprocal ohms at oo C. T h e specific conductivity of the solvent is given at the head of each table. In computing the values of A the conductivity of the solvent has not been subtracted. Any one desiring to deduct the conductivity of the pure solvent' will find all necessary data for that purpose in the tables.
TABLEI FeCI, (Sp. cond. HCN = 4.07 X U
4-17 7-24 IO.
78
22.87 33.12
IO+)
i
h
7J
-~.
111.7 135.5 145.8 152.4 154.0
75.5 119.1 431.1 1042.0
i I
1
'
174.7 181.5 213.7
1
TABLE2
TABLE3
SbCI, (Sp. cond. HCN = 1.42 X
10-5)
BiCl, (Sp. cond. HCN = 3.5 X
U
A
U
A
0.709
0.77
4.526' 7.273 20.24 81.31
6.67 4 89 3-13 4.32
269 30 123 6.188 28.08 2..
0.41
0.40 0.45
I . 19
10-j)
The practice of deducting the conductivity of the pure solvent from that of the solution is, to say the least, open to serious question. Solution probably slightly supersaturated.
Ii
31.08 104.8
I6.O1 17.49
I
' I
160.7
259.6
I
TABLE 6
TABLE7
N H ( C6H,,)CS.SNH,(C,H,,) (Sp. cond. HCN-4 07 X IO-^)
KI (Sp. cond. HCN = 4-07 X IO-^)
-
V
83.7
12.04
127.4
27.07
5.559 12.70
160.3 194. I 208.3 223.3 227.5 238.7
23.58 53. '7 91-37
16j.g
244.9 600.0
TABLE8 KC NO^
I 262
I
I
254.1
278.0 300.4 308.2 324.8
81-57 212.6 452.5
TABLZg
(Sp. cond. HCN = 1.0X IO-^) v
A
~
KCNS (Sp. cond. HCN = 1.0X IO-^) I
A
V
284.0
1.679 2.799 5.826 22.20
-
A
1
11
1
132.1 169.3 214.1 275.1
The saturated solution of this salt has a sp. cond. of 0.00384. I t contains less than 40 grams of AgNO, per liter. The sp. cond. of the saturated solution is 0.007g7. The saturated solution has a sp. cond. of 0.00233.
L. Kahlenberg and H. Schlundt
454
TABLEI O
TABLE11
KNO, (Sp. cond. HCN = 0.89 X IO-^)
K,CrO,Z (Sp. cond. HCN = 3.6 X IO-^)
I'
TABLE1 2 KMnO, (Sp. cond. HCN = 1.4 X
II
IO+)
TABLE13 NH,CI (Sp. cond. HCN = 1.4 X
1 0 ~ ~ )
V
142.I 214.1 263.5 310.5 340.2 511.0
TABLE14
66.15~
-
191.3
1
TABLE15 Pyridine, C,H,N Amyl amine, (C,H,,)NH, (Sp. cond. HCN = 1.4 X ro--S) I(Sp. cond. HCN = 0.752 X IO-$) (Sp. cond. C,H,,NH, < 1.9 X (Sp. cond. C,H,N < 2 X IO-^) I
IO-^):1)_.-
__ ___
I
0,2698 0.4977 0.954
36.8
2.203
55.1
5.733 15.80
8.86
24.5
78.2 109.4
1
0.1370 0. I go6 0.3026 0.5070 0.7798 1.858 7.455
0.038 0.106 0.1q0
0.320 0.344
0.500
0.792
This solution was nearly saturated. A saturated solution was found to have a sp. cond. of 0.1754. The saturated solution has a sp. cond. of 0.0084. This solution was nearly saturated. The sp. cond. of the saturated solution is 0.026. This solution was very nearly saturated.
Conduciivity in Liquid Hydmcyanic Acid
57.6 87.4
33.3 88.0
TABLE18 Acetic acid (Sp. cond. HCN ==4.07 x IO-') (Sp. cond. acetic acid < 2 x 1 0 - ~ ) 1 A
V
0.0883 0 . I 208 0.4325 1.371 10.52
0.0016 0.0045
0.0233 0.0798 0.623
455
1
I
155.2 592.5
~
84.2 99.9
1
TABLE19 Cyanacetic acid3 (Sp. cond. HCN = 2.13 X IO^) 1 1, V A I1
I1
1~
1~
0.2378 0.4231 20.14
0.146 0.22I
0.812
(i
TABLE2 0
TABLE2 1
Trichloracetic acid (Sp. cond. HCN -- 1.4 X IO-')
Trichlorlactic acid4 (Sp. cond. H C N = 1.8 X IO-^)
V
A
I
A
V
I'
0.3990 0.5588 I .062 2.402 6.068 36.59
0.068 0.087 0.128
4.617 48.72
~
0.367 2.42
0.210
0.359 I .a09
The saturated solution has a sp. cond. of 0.00273. A saturated solution contains nearly I gram-molecule in 26 liters and has a sp. cond. of 0.00131. The sp. cond. of the saturated solution is 6.12X 109. The saturated solution has a sp. cond. of 1.31 X IO-^.
456
A
V
c .8066 1.567 2.708 19-33
0.021
0.041 0.07 I 0.495
5 * 7oa 8.55 8-55
64.4 (after two hours) 75.8 (initially)' 89.1 (after 75 minutes) 17. T O 113.9 (after 2 hours) Hydrochloric acid. (Series 2) ('Sp. cond.. HCN = 0.54 X IO.-^) V
~
-r
A
14.56 (initially)3 74.3 (after two hours)
16.67 16.67
~~
1 ~
398 44.9 71.9 91.6
(initially)' (after 15 minutes) (after 30 minutes) (after several hours)
The saturated solution has a sp. cond. of 2.6 X IO-^. This solution had a sp. cond. of 0.0113, while a saturat'ed solution showed a sp. cond. of 0.128. This will serve to give an approximate idea as to the extent to which HC1 is soluble in HCN. The determinations marked " initially " were made as soon as the gas was completely absorbed. As the absorption was not performed in the same length of time in the different series the figures are, of course, not really comarable.
Conductivity in Liquid Hydrocyanic Acid
457
TABLE24 Sulphuric acid (Sp. cond. HCN = 0.8 X IO-' The sulphuric acid used had a sp. gr. of 1.840 at 20' and therefore, according to Winkler's tables, it contained 94.79 percent H,SO,, or 77.38 percent SO,. Grams of this acid in
IOO
Sp. cond. X xoS
cc. solution
0.520
5.75 9.98 13.06
1.688 4.584 10.086
1.226 11.53 4.855 18.62 i I 5.60 The sulphuric acid itself T h e solutions of known strength of hydrochloric acid in liquid hydrocyanic acid were obtained by filling a gas burette with hydrochloric acid gas thoroughly dried with concentrated sulphuric acid and finally with phosphorus pentoxide, and causing a measured volume of the gas to be absorbed in the liquid hydrocyanic acid contained in the resistance cell above described at 0'. T h e graduation on the cell permitted the volume of the solution to be read. T h e gas was forced out of the burette by means of dry metcury, a very fine capillary tube running from the burette to the bottom of the column of liquid hydrocyanic acid in the cell. T h e gas was displaced very slowly and the absorption was quite complete. Exposure to the air was avoided as much as possible, but it is not claimed that the solution was ~
~
458
L. Kalzlenbevg and H. Schlundt
absolutely free from traces of moisture. Presence of moisture would elevate the conductivity, and therefore the results in Table 23 are probably a trifle too high. It will further be noted that i n Series 2 of Table 23, where the HCN had the lowest sp. cond., the solutions also had the lowest conductivity ; and furthermore, the solutions in Series I had the highest conductivity, and the HCN used in this series also had the highest conductivity. T h e conductivity of solutions of HC1 in liquid HCN moreover increases with lapse of time, showing that the speed of the reaction which goes on can readily be measured. I t was not our purpose to investigate the rate of this reaction. We simply desired to ascertain approximately how well solutions of HC1 in liquid HCN conduct as coinpared with corresponding aqueous solutions. T h e results are entirely sufficient to show at a glance that HC1 in liquid HCN is a much poorer conductor than HC1 in water. KO attempt was made to prepare a sulphuric acid corresponding exactly to the formula H2S04,that is to say one that contained 81.63 percent SO,. In the one case (Table 24) the sulphuric acid dissolved in liquid HCN contained 77.38 percent SO,, in the other case 83.46 percent SO,. T o compute inolecular conductivities in these cases was not attempted. T h e specific conductivities given in the table are sufficient to indicate that sulphuric acid in liquid HCN is a niucli poorer electrolyte than comparable solutions of sulphuric acid in water. An inspection of Tables I to 24 shows that the potassium salts investigated, namely, KI, K N 0 3 , KCXS, KMn04, K2Cr04, KCNO, (Tables 7 to 1 2 ) are most excellent electrolytes when dissolved in liquid HCN. K I and K N 0 3 have a molecular conductivity in liquid HCN which is over 3.5 times as great as that of the corresponding aqueous solutions at the same temperature.' T h e conductivity of aqueous solutions of KCNS, KMn04,K2Cr04, and KCNO have apparently not been investigated at oo ; but the conductivity of these salts in liquid HCN even at ooexceeds For comparison see the mol. con. of these salts in aqueous solutions at oo in Jour. Phys. Chem. 5, 348 (1901).
Conductivity in Liquid Hydrocyanic Acid
459
their conductivity in aqueous solutions at 2 j".' T h e conductivity of NH4C1 (Table 13) also exceeds that of corresponding aqueous solutions at 18" ; and the same is true of Ag2S04.' NH(C5HIJCS.SNHg(C5HrI), Table 6, also has a high conductivity in liquid H C N ; though the conductivity of aqueous solutions of this salt has apparently not been determined, i t would seem that the figures would probably not reach the magnitude of those in Table 6. T h e high conductivity of the solutions mentioned in the preceding paragraph, as compared with the conductivity of the corresponding aqueous solutions, might tempt one to draw the conclusion that the Nernst-Thomson rule is indeed verified in case of the solvent, liquid HCN, inasmuch as its high dielectric constant would lead one to expect a conductivity exceeding that of comparable aqueous solutions.3 But all such ideas are a t once dispelled by a further consideration of the remaining substances in the foregoing tables. So i t appears a t a glance that acids (Tables 18 to 24) dissolved in liquid H C N are incomparably poorer electrolytes than the corresponding aqueous solutions.+ Silver nitrate (Table 4) in liquid H C N conducts only about one-fourth as well as in aqueous solutions of the same strength a t o O . 5 Ferric chloride in liquid HCN (Table I ) conducts less than half as well as the Corresponding aqueous solutions of this salt a t 25" ;6 so that it seems likely that the aqueous solutions of this salt at oo will conduct better than those in liquid HCN. Again SbC13 and BiCI3 (Tables 2 and 3) are poor electrolytes in H C N ; a comparison with aqueous solutions is of course impossible in these cases as the salts are decomposed -
Coinpare Kohlrausch and Holborn. Leitvermogen d. Elektrolyte. Compare tables in Ostwald's Lehrhuch d. allgem. Chem. 2, 756, 771. M. Centnerszwer (1. c.) found K I and S(CH3),I to conduct better in liquid HCN than in water and drew such a conclusion. While the conductivity of these acids in aqueous solutions at oo has apparently not been determined, the values in liquid HCN are so very low as to admit of tliis conclusion. I n fact, if the conductivity of the pure HCN were subtracted from that of the acetic acid solutions the remainders would in several cases be negative in sign. Compare Jour. Phys. Chem. 5 , 348 (1901). Compare Goodwin. Zeit. phys. Chem. 2 1 , 3 (1896).
460
L. Kahiknbevg and H. Schlundi
into oxychlorides by water. T h e relatively high conductivity of amyl amine, strychnine and morphine in liquid HCN (Tables 14,16, 17) is worthy of note. These bases undoubtedly react with the liquid HCN, forming salts that dissolve in excess of the solvent ; the action in the case of amyl amine is violent in character, being accompanied with liberation of much heat. Pyridine (Table I 5) forms very poorly conducting solutions, though it probably also unites chemically with the solvent. T h e facts are then, that while some salts dissolved in liquid H C N conduct electricity better than in water, many others conduct much poorer than in their corresponding aqueous solutions. T h e acids as a class illustrate this in an especially striking manner ; for while their aqueous solutions are most excellent electrolytes, their solutions in liquid H C N are only moderately good electrolytes in the case of HC1 and H2S04,while the solutions of the organic acids are exceedingly poor conductors of electricity. I n the face of these facts, the Nernst-Thomson rule can clearly not be considered as substantiated by the conductivity of solutions in liquid HCN. A comparison with the conductivity of liquid ammonia solutions shows that K N 0 3 , NH4C1, and K I are better electrolytes in liquid ‘HCN than in liquid ammonia ; * on the other hand, AgN03 is a much better conductor in the latter solvent than in the former. Solutions of KI and K C N S in liquid H C N are much better electrolytes than the corresponding solutions in liquid SO,.3 While in some cases, like KI and K N 0 3 (Tables 7 and IO), the molecular conductivity increases but slightly with the dilution, as it does in the corresponding aqueous solutions, in other cases like KCNS, K M n 0 4 and K2Cr04 (Tables 9, 1 2 and 11) this increase is very considerable, exceeding by far that in the aqueous solutions. These statements hold even if the conducThis is the*secret of the solubility of so many of the alkaloids in liquid HCPU’. Kraus
Compare Cady. Jour. Phys. Chem. Amer. Chem. Jour. 24, 87 (‘goo). Compare Walden and Centnerszwer.
I,
712 (1897) ; also Franklin and Zeit. anorg. Chem. 30, 168( 1902).
Conductzvity in Liquid Hydrocyanic Acid
'
461
tivity of the liquid HCN used as solvent be deducted from the conductivity of the solutions, as is commonly done in the case of aqueous solutions. Again, the molecular conductivity of A g N 0 3 (Table 4) changes but slightly with the dilution, which is also true of aqueous solutions of this salt; although as has been remarked, the latter are much better conductors than the HCN solutions. In the case of BiC13 (Table 3) the molecular conductivity passes through a minimum ; or, if the conductivity of the solvent be deducted, the molecular conductivity would decrease as the concentration decreases. When the results of the conductivity measurements of the solutions in liquid hydrocyanic acid are regarded in connection with the conductivity of aqueous solutions, liquid ammonia solutions, solutions in liquid sulphur dioxide, etc., it becomes evident that the conductivity of a solution is not determined by the dielectric constant of the solvent, its state of polymerization or its spare valences, but rather by the specific nature of the compound formed when solute and solvent act on each other to form the solution. Only a very limited number of tests of chemical action in solutions in liquid HCN were made. Metallic sodium and metallic potassium act upon thoroughly dry liquid HCN, forming hydrogen and the cyanides of the metals; the latter are soon coated over with the white salts which are practically insoluble in liquid HCN. Metallic magnesium and sodium carbonate are not attacked by liquid HCN. A solution of SO3 in HCN, though it conducted well (having asp. cond. of 0.0066), nevertheless did izot act in the least on dry magnesium, zinc, calcium carbonate or potassium carbonate. Fuming sulphuric acid of sp g r 1.898 at 20°, when dissolved in liquid HCN' attacks magnesium, zinc (amalgamated as well as plain), and potassium carbonate, but does not act on aluminum, cadmiurh, iron, copper, silver, lead, platinum, or calcium carbonate. But when cadmium is placed in the solution in contact with platinum, hydrogen is evolved on the platinum. On the other hand, iron, aluminum, The solutions used were those in Table 24.
462
Conductivity in L i p i d Nydmcyaizic Acid
copper, lead and silver are not attacked by the solution even when in contact with platinum. Hydrochloric acid solutions in liqoid HCN attack magnesium and also zinc (amalgamated as well as plain). Cadmium is also attacked, but very slowly. Zinc or cadmium when placed in contact with platinum in the solution, cause hydrogen to be evolved mainly on the platinum as in the corresponding aqueous solution. Hydrochloric acid dissolved i n liquid HCN does not attack aluminum, iron, lead, copper, silver, platinum, sodium carbonate, sodium bicarbonate, calcium carbonate or barium carbonate. Solutions of trichloracetic acid in liquid HCN attack metallic magnesium and sodium carbonate, but not calcium carbonate or zinc, even when the latter is in contact with platinum. Yet Table 2 0 above shows that trichloracetic acid in liquid HCN is an electrolyte, though to be sure not a very good one. Trichlorlactic acid dissolved in liquid HCN does not attack magnesium of zinc, while cyanacetic acid in solution in liquid HCN does act on magnesium. Phosphorus trichloride, thionyl chloride, sulphuryl chloride and amyl amine react violently with liquid HCN.
-
Laboratory of Physical Chemistry, University of Wisconsin, Madison, Wis., July, 1902.
