1654 (2x1.-Molecular Conducthity of Amidosulphonic acid. By J ~ J I SAKURAI, D.Sc. (Japan), Professor of Chemistry, Imperial University, Japan. A r the request of Dr. Divers, I have determined the molecular conductivity of amidosulphonic acid. The apparatus which I used for the purpose consisted of a Kohlrausch’s universal bridge, in which the measuring scale is so graduated that the index at once gives the ratio of the lengths of the arms. The essential parts of the whole arrangement are sketched out in the accompanying figure. The primary current from two Daniell’s elements, e, enters the induc- tion coil i ; the induced current divide8 at c (or d), one part passing through the solution s, and the other through the rheostat T , both to return to the coil through d (or c).ha is the measuring wire along which the index, d, is moved, until the telephone, f, no longer speaks, a t which point we have, for the resistances of the various pasts the following relation : s : r :: bd : ad or s = adlbd x r. Since the index, d, at once gives the ratio, bdlad, the resistance of the vessel containing the solution is obtained by multiplying the resistance of the rheostat by this ratio. In all the determinations, I so arranged the resistances that the index should always lie between 0.9 and 1.0 division on the scale when the telephone was silent ; in this manner, any inaccuracy arising from possible errors of calibra- tion was reduced to the minimum. This part of the scale is sub- divided into 10 parts, and it is easy to read to one half of these divisions.Instead of attempting to catch the sound minimum of the telephone, I determined the limits of the region of silence, and took the arithmetical mean of these limits as the true sound-minimum, as, for example, 0.935-0.975 = 0.965. For each dilution, I made two sets of determinations by slightly altering the resistance of theMOLECULAR CONDUCTIVITY OF AMIDOSULPHONIC ACID. 1655 rheostat, each set consisting of two separate readings, and took the mean of these four readings. The resistance vessel employed for holding the solution is of the Arrhenius form, and was made by following the directions given by Ostwald (Handbuch fur physiko-chemisehe Messwagen). Burettes and pipettes were also accurately calibrated according to the methods described in the same valuable work.The temperature at which the determinations were made was 25.00-25.05° throughout, this constant temperature being main- tained in a water thermostat worked by a small turbine. Resistance Capacity of the VesseZ.--E'or determining the resistance capacity of the vessel, I employed N/50 soIution of potassium chloride, the specific conductivity of which is accurately known to be X = 2.594 x If Z = the measured conductivity of the vessel containing N/50 solution of potassium chloride, and c = its resistance capacity, then c = X/Z. The results obtained are given below, in which r = resistance of the rheostat and R = ratio of the two arms of the scale, bdlad. at 25". R. I 1 r . (1). (2). Mean. r.R z- 111. 155 0.955-0.975 = 0.9650 0.955-0.975 = 0.9650 0.9650 149.58 156 0 -950-0 '970 = 0 '9600 0 *950-0*965 = 0 '95'75 0 -9588 149 '5'7 157 0 *940-0*965 = 0 -9525 0 -945-0 -960 = 0 -9525 0 -9525 149 *54 158 0 '935-4 '960 = 0' 9475 0 *935-0 '955 = 0 -9450 0.9463 149 '52 159 0 *930-0 *950 = 0 '9400 0.930-0'950 = 0 -9400 0 -9400 149 -46 160 0,925 -0 '945 = 0 -9350 0' 925-0 '945 = 0 '9350 0 *9350 149 60 Mean..149 *55 Hence, c = h,/Z = 2.594 x loe3 x 0.14955 x lo3 = 0.387933. Specific CGnductivity of Water.-Taking advantage of the cold weather at the time, the distilled water employed for making and diluting the solutions was purified by freezing a portion of it, the ice formed being melted and used in all the determinations. Its specific conductivity was determined with the following results : 9.. R. r.R = 111. 10,000 18-22 = 20.0 200,000 11,000 17-22 = 19.5 204,500 Mean..202,250 -- 1 LU2,250 Hence, h = c.Z = 0.387933 x = 1.9 x As the molecular conductivity of the solutions was determined for v = 32, 64, 128, 256, 512, and 1024 litres, the corrections for the conductivity of -water for the respective dilutions are 6, = 0.06, 0.12, 0.24, 0-49, 0.97, and 1.94; 5 T B1656 SAKURAI : MOLECULAR CONDUCTIVITY these corrections being obtained by multiplying the specific conduc- tivity of water, as determined above, into the molecular volume of the respective solutions, expressed in cubic centimetres. No account was taken of these corrections in the case of the molecular conduc- tivity of amidosulphonic acid, inasmuch as the latter is of a very considerable magnitude when compared with these ; moreover, it is difficult to know whether the impurities in water increase or diminish the conductivity of the acid.In the case of the sodium salt, the above corrections were duly deducted from the observed molecular conductivity. Molecular Conductiiiity of Ainidosulphonic acid.-An N/32 solution of the pure acid (NH2SOsH = 97.11) having been made by dissolving 0.1517 gram in 50 c.c., 20 C.C. of it was transferred to the resistance vessel, and, when a constant temperature of 25' had been attained, a set of conductivity determinations were carried out, with changes of resistance, in the manner already stated. Then 10 C.C. of tho solution was removed from the vessel and replaced by water, and another set of determinations made, and so on, until the strength of the solution was reduced to N/1024.The results are tabulated below, ZI being the molecular volume of the solution in litres, and T and R having the same meaning as before. R. r------------ - 21. r. (1). (2). Mean. T . R = l/t. 32 44 0.9.u)-0*965 = 0.9525 0*945-0*965 = 0'9550 0.9538 41.97 ,, 45 0 *915-0 '950 = 0 -9325 0 *920-0 *945 = 9 *9325 0 *9325 41 -96 - Mean.. 41'97 64 80 0.950-0.975 = 0.9625 0*950--0*975 = 0.9625 0.9625 77.00 ,) 82 0 '930-0*950 = 0 -9400 0.930-0 *950 ;= 0 '9400 0 .&400 77 '08 - . Maan.. 77-04 128 150 0 -956-0 -980 = 0 -95'75 0 -955-0 '980 = 0 -96'75 0.9675 149 '13 ,, 152 0 -945-0 *965 = 0.9550 0 '9454 *970 = 0 -9575 0,9563 145 -36 - Mean. . 145 '25 256 290 0,945-0 -965 = 0 -9550 0 *940--0 '965 = 0 -9525 0 '9538 276 '60 ,, 294 0 -925-0 '950 = 0 *9375 0 *930-0.955 = 0'9425 0 *9400 276 *36 Mean..25'6 -48 612 570 0 -950-0 '9'75 = 0 -9625 0 *950-0*975 = 0 -9625 0 *9625 548 '63 ), 680 0 '9304 9% = 0 -9425 0.935-0'965 = 0 -9500 0 '9463 548 *86 Mean. . 548 -74 ), 1140 0*940-0*965 = 0.9525 0.930-0.970 = 0.9500 0'9512 1084.39 Mean.. 1084 '00 1024 1120 0.955-0 '980 = 0 -9675 0 '955-0 '980 = 0.9675 0 -9675 1083 -60 __I-OF AMIDOYULPHONIC ACID. 1657 The moleoular conductivities, pw, of amidosulphonic acid for the respective dilutions are, therefore, p32 = 0.387933 X 32/0.04197 = 295.78 p64 - ,, x 64/0.07704 = 324.86 Plzs = ?, x 128/0.14525 = 341.87 D256 = ,, x 256/027648 = 359.20 p512 = ,, X 512j0.54874 = 361.95 /4024= ,, x 1024/1.08400 = 366.46 The molecular conductivity of the acid at infinite dilution, pa, has been calculated from that of the sodium salt.Molecular Conductivity of Sodium Amidosulph0nate.-A solution of pure sodium hydroxide, prepared from metallic sodium, was made, titrated witb pure and crystallised oxalic acid, and made up to N/32, phenolphthale'in being used as the indicator. About 30 C.C. of this solution was carefully neutralised with powdered amido- sulphonic acid, with addition of a trace of phenolphthaleyn, and filtered with the usual precautions. Then 20 C.C. of the neutral solution was transferred to the resistance vessel, and conductivity determinations were made in exactly the sane manner as with the acid. R. u. r. (1) (2) Mean. T . R= lil. [Po0 = 3 73-97]. The results are as follows : -7 r--------.A- -- 32 155 0 -945-0 -960 = 0 -9525 0 *935-0 -960 = 0 -9475 0 -9500 147 '25 ,) 156 0 '935-0 '955 = 0 -9450 0 '9304) '955 = 0 '945 0 -9438 147 '23 - Mean .. 147 '29 64 395 0 '940-0 -975 = 0 '9575 0*945-0*970 = 0 '95'75 0.9575 282 -46 fi 300 0 -92,- '960 = 0 -9925 0 *930--0 *960 = 0 -9400 0 -9413 282 -39 Mean . . 282 -43 128 570 0 950-0 '970 = 0 *9600 0 -9504 '9'70 = 0 .MOO 0 '9600 547 '20 ,, 575 0 '945-0 '960 = 0 -9525 0 '940-0 -960 = 0 '9500 0,9513 547 -00 Mean . . 547 -10 256 1130 0 094-0 -960 = 0 '9800 0'940-0 '960 = 0 *9500 0 -9500 1073 -50 ,) 1140 0 '930-0 '955 = 0 -9425 0 '925-0 '9.55 = 0 *9900 0,9913 1073 '08 -- Mean . . 1073 -29 612 2200 0 '935-0 '9170 = 0 '9525 0 *93O-c~9'70 - 0 -9500 0 '9513 2092 '86 ,) 2240 0 '91- '955 = 0 -9350 0.915--0*935 = 0 '9350 0 '9350 2094 -40 -- Mean .. 2093 -63 1024 4300 0 -950-0 *970 = 0 -9600 0 .W-O -970 = 0 -9550 0 '95'75 4117 '25 ), 4400 0 '925-0'950 = 0 '9375 0.925-0 -955 = 0,9350 0 -9363 4119 '72 -- Mean .. 4118'491658 SAKURAI : MOLECULAR CONDUCTIVITY The molecular conductivity of sodium amidosulphonate is, there- fore, %J* PV. ~ 3 2 = 0,367933 x 32/0*14724 = 84.31 0.06 84.25 /&it = ,, x 64,’0*28243 = 87.91 0.12 87.79 PI28 = ,, x 128/0*54710 = 90.76 0.24 90.52 p256 = ,, x 25611.07329 = 92.53 0.49 92.04 p512 = ,, x 512/2.09363 = 94.87 0.97 93.90 PI024 = Y, x 1024/4v11849 = 96.45 1.94 94-51 It may be observed that the difference, plM - b2 = 10.26, is of the same magnitude as that in the case of the sodium salts of all the monohasic acids, showing that the ions of amidosulphonic acid are XI and NH2S03.For calculating the molecular conductivity of sodium amidosulphonate at infinite dilution, I have made use of Bredig’s table (Zeits. physikal. Chem., 1894, 13, 198), which gives a more concordant result than the use of Ostwald’s values. v : 32 64 128 256 512 1024 d,: 14 11 8 6 4 3 pv : 84.25 87.79 90.52 92.04 93-90 94-51 pCa : 98.25 98.79 98.52 98.04 97.90 97.51 Mean 98.17. The velocity of migration of the Na ion being 49.2, that of the NH2B03 ion is 98.17 - 49.2 = 48.97 ; and the velocity of migration of the H ion being 325, the molecular conductivity of amidosulphonic acid a t infinite dilution, pa, is evidently 325 + 48.97 = 373.97. Discussion of the Besults.-The velocity of migration of the anion, NH,SO, = 48.97, approaches those of Br03 = 50.5 and F = 50.8; it is much greater than that of 10, = 37.9 or HZPOa = 33.5, and much less than that of C1 = 70.2, Br = 73.0, I = 72.0, or NO3 = Wl.Among the organic anions, that of formic acid, HCO, = 31.2, is the only one which exceeds NH2S03 in velocity. The ‘‘ strength ” of amidosulphonic acid may be judged of from the degree of its dissociation, pzt/,uLao = rn. The following table, in which 100 times this ratio is calculated, shows that amidosulphonic acid is already dissociated to the extent of 79 per cent. in a, K/32 solution, and that the degree of dissociation attains 98 per cent. in n N/1024 solution Amidosulphornic acid (pa = 373.97) t’: 32 64 128 256 512 1024 pV : 295.78 324.86 341.87 359.20 362.95 366.46 loom : 79.09 86.87 91.42 96.04 96.79 97.99 Amidosulphonic acid may, therefore, be ranked among the strongOF AMIDOSULPEONIC ACID. 1659 mineral acids, being nearly comparable with iodic acid, as may be seen from the following numbers : 100 nz.I------- 6. H,NH,SO,. H,I$ 32 79-09 84.60 64 86-87 90.11 128 91.42 93.96 256 96-04 95.89 512 96-79 97.27 1024 97-99 97-55 In its constitution, amidosulphonic acid is sulphurous acid in which the H directly combined with sulphur has been replaced by the group NH2 : Sulphurous acid. Amidosulphonic acid. Now it is evident, from the measurements of Ostwald (J. pr. Chem., 1885, 32, 314) and of Barth (Zeits.physika7. Chern., 1892, 9, IN), that sulphurous acid, in point of electric conductivity, behaves as a monobasic acid, its ions being H and HSO,. It is, therefore, possible to obtain a knowledge of the inffuence of the replacement of H by NH, on the strength of the acid, by comparing together the values of 100 m.of sulphurous and of amidosulphonic acids. Determinations of the electric conductivity of sulphurous acid, as well as of metallic sulphites, are, however, attended with considerable inaccuracy, owing to the unavoidable and rapid oxidation occurring during the deter- mination. The following are the numbers obtained by Barth (Zoc. cit.) at 25’: v = 32 64 128 256 512 1024 Sulphurous acid, H,SO,H.. . . 177.5 214 ‘9 248 -5 279.0 303 -3 524 -7 Hyd. sod. sulphite, Na,S03H.. 80 *9 84 *7 88 *7 92 *5 95 -8 98 ‘8 The difference, pi024 - “32, for the sodium salt, instead of being about 10, is as high as 17.9, this error arising from the partial oxidation of the sulyhite into sulphate; the numbers obtained by Barth are, consequently, admittedly too high, the higher as the soln- tion is the more dilute.We have, therefore, no means of calculating exactly the velocity of migration of the anion SO,H, but it may be approximately taken as (80.9 + 14) - 49.2 = 45.7, 80-9 being the value of pa for the aodium salt, 14 Bredig’s constant for this dilution, and 49.2 the velocity of migration of the kation Na. The approxi- mate molecular conductivity of sulphurous acid at infinite dilution is, therefore, ,urn = 325 +- 45.7 = 370.7, and the values of 100 pa/pa0 for this acid at the respective dilutions are :1660 SAKURAI : MOLECULAR CONDUCTIVITY 2, = 32 64 128 256 512 1024 100m = 47.88 57.97 67.04 75.26 81.8% 87.59 The increase of dissociation with dilution, as thus calculated, is admittedly too great, inasmuch as the oxidation of sulphurous acid gives increasingly too high values of ,up.Taking this fact into con- sideration, and comparing the above numbers with those obtained for amidosulphonic acid : v = 32 64 128 256 512 1024 100m = 79.09 86.87 91.42 96.04 96.79 97.99 it becomes evident that umidosulphonic acid is much stronger than suQhu~ous acid. This conclusion, drawn from the study of the electric conductivity of amidosulphonic acid, is interesting from the fact that the influence of the NH, group on the strength of oyganiic acids generally is quite of the opposite character. Thus, from the data given by Ostwald (Zeits. physikal. Chew., 1887, 1, 74), I have calcu- lated the following values of 109 m.fGr benzenesulphonic acid : et = 32 64 128 256 512 1024 100 m = 90.91 93.95 96.15 98.52 99.61 100.00 Benzenesulphonic acid is thus one of the strongest acids, whilst its amido-dcrivatives are far below it in strength, as may be seen from the following numbers (Ostwald, Zeits. physi2aE. Chem., 2889, 3, 406) : 100 m. Ortharmdobenz. Me tamidobenz. Paramidobenz. V . sulphonic acid. sulphonic acid. aulphonic acid. f--7--- 7 32 - - 12.79 64 SG.6 10.25 17.52 128 47.1 14.26 23.80 256 58.5 19-70 31-SO 512 69% 26.55 21.60 1024 80.0 34.70 53.00 Again, benzoic acid is stronger than its amido-derivatives, and acetic acid, though itself a very weak acid, is yet incomparably stronger than glycocine. These are facts already well established (compare J.Walker, Proc., 1894, 137). The striking contrast between the influence of NH, on the strength of organic acids generally, and that on sulphurous acid-the only inorganic acid of which the electric conductivity of the amido- derivative has been determined-has, in all probability, to be ac- counted for by the circumstance that, in the former, the basic group -R"*NHz acts on -COOH or -SOsH, forming internal ammoniam salts, as wag first suggested by Erlenmeyer (compare J. Sakurai-;01' AMIDOSULPHONIC ACID. 1661 " Constitution of Glycocoll and its Derivatives," JOW. Rc. CoZZ., Imp. Fniu., Japan,, 7; or Proc., ;1894, 137). Indeed, Ostwald, after determining the molecular conductivihy of glycocine, and finding that it increases only very slightly on dilution, goes on to remark : " The nature of this series of numbers is rather that of a neutral salt, and the conclusion already drawn from the neutral reaction of glycocinc, that it is a salt-like compound, is confirmed by the electri- cal measurements " (J.pr. Chem., 1885, 32, 369). In another paper, the same author speaks of amidoacetic acid as one " which can no longer be called an acid " (Zeits. physikal. Chern., 1889, 3, 189). I have shown in another place (Zoc. cit.) that the conclusion is inevitable, that not only glycocine, but organic amido-acids generally, are salt-like compounds ; the study of the electric conductivity of amidosulplionic acid has confirmed this view by showing that the mere presence of NH2 does not diminish the strength of an acid, and that the fact, therefore, that organic amido-acids are weaker than the non-amidated acids must be explained by assuming the nitrogen of the basic group, -R"*NH2, to be in combination with the hydrogen of the acid group, -COOH or -S03H, thus : H3N*R"*CO*0 or H3N*R"* S 02*0, the dissociation of these molecules into H, on the one hand, and L---I L - 2 H2N*R".C0*O or H2N*R"*CO*0, on the other, occurring to a much L A L I less extent than in the case of non-amidated acids, which dissociate into H and R * C 0 2 or R'*SO,.It may be observed that the intro- duction into organic amido-acids of a group that diminishes their salt -like character must facilitate their dissociation, and thus increase their conductivity and strength. The superior conductivity of aceturic and hippuric acids, as compared with that of glycocine, may be cited in favour of this view.The Lmu of Dilution.-As is well known, Ostwald's dilution formula- which expresses the relation between conductivity, pv, and dilution v, oE eiectrolytes which are only moderately dissociated, does not, apply in the case of highly dissociated electrolytes. Now, Rudolphi has shown (Zeits. physikat. Clzenz., 1895, 17, 315) that the following empirical formula well expresses this relation : and, further, van't Hoff (Zeits. physikal. Chem., 1896, 18, 300) has1662 LOEW : PHFSIOLOaICAL ACTION pointed out that the relation may be equnlly well expressed by altering Rudolphi’s formula into K = Pa which may be written as I( = C?/CS3, 1 where &!- . - = Ci is the concentration of the ion, and r , v (1 -E!.)L ,v = c, is that of the undissociated salt. I have tested the above formulae wit>h sodium amidosulphonate ; tlhe results which are tabulated below are in agreement with both of them : Xodium Amidosulphonate (pa = 98.17). z1 = 32 64 128 256 512 1029 pD = 8425 87.79 90.52 92.04 93.90 94.51 KR = 1.00 1-03 1.05 0.96 1.01 0.85 KH = 1.00 1.01 1-01 0.92 0.96 0.80 The values of K, and KH have been calculated according to Rudolphi’s and van’t Hoff’s formulae, respectively, the value found for z1 = 32 litres being, in both cases, made equal to 1. The results are almost equally constant u p to v = 512 litres, but, in both cases, there is a greater deviation for the last dilution, owing, no doubt, to a greater experimental error.