N E G A T I V E VISCOSITY.
7 21
approximately equal, as was found to be true in all other cases for which this calculation has been made. 4. Precision Discussion,
The term z E F in formula (3) amounts to 79,040 calories, the second term t o only 4600 cal., from which it is evident that even a large error in the vapor pressures would have only a relatively small effect on the final result. Assuming an error of 0.1 mm. in Psol, p , and 0.1 mm. in p , which seems an outside limit, the resultant effect is 600 calories, or about 0.8 per cent. error in A F . Assuming a possible error of 0.02 volt in E the combined error in AF would be 990 cal., or 1 . 3 per cent.
5 . Summary. The free energy A F of NiCl, was determined by measuring the potential of the cell. Ni 1 Sat. sol. of NiCl,.6H20 1 C1, Pt. A formula for AF was deduced, involving this potential, the vapor pressure of the saturated solution, of the system NiC1,.6H,O-NiC1,.2H,O and of NiC1,.2H20-NiCl,. The pressure of the last system was obtained both by direct and by indirect measurement. The free energy and total energy of NiCI, were found to be approximately equal.
+
ELECTROCHEMICAL LABORATORY, MASS. INST. O F TECH., BOSTON.
A STUDY OF THE SOLUTIONS OF SOME SALTS EXHIBITING NEGATIVE VISCOSITY, FREDERICK H. GETMAN. Received March IO, 1908.
In 1873 Hiibner' determined the viscosities of a series' of solutions of alkaline halides of equal densities and observed that some of the salts diminished the viscosity of water. Subsequently Sprung2 made an extensive study of the viscosities of saline solutions between the temperatures o o and 60' C. He divided the salts examined into two groups as follows: ( I ) KC1, KBr, K I , KNO,, KClO,, NH,Cl, NH,Br, ",NO,. ( 2 ) K,SO,, NaCl, NaBr, NaI, NaNO,, NaCIO,, Na,SO,, (NH,),SO,, RaCI,, SrCI,, CaCI,, LiCl, MgSO,. He pointed out that a t low temperatures the salts of the first group lower the viscosity of water and a t higher temperatures they increase it. The salts of the second group always increase the viscosity of the solvent, the viscosity of the solution becoming less as the temperature is raised.
' POgg. Ann., 157, a
Ibid., 159, I .
130.
--
FREDERICK H. GETMAX.
-I 7 7
The experimental work of Sprung was later confirmed by the invcsti gations of Slottc' and Wagner,2 the latter having studied the viscosities of the solutions of forty different salts a t selwal concentrations. . i r r l i e n i u ~ ,Kanitz4 ~ and Niitze15 have measured the viscosities of saline solutions which show the phenomenon of negative viscosity and still more recently Ranken and Taylore have made some extremely accuratr. determinations of the viscosities of solutions of potassium chloride and ammonium iodide a t difierent temperatures. One of the first to offer an explanation of negative viscosity was Euler,' who made use of the theory of electrostriction proposed by Nernst and Drude.8 In terms of this theor!- the ioiis are enveloped in a strong electric field, owing t o their charges, and the intervening liquid is subjected t o great stress, so that the tendency of the ions to increase the viscosity in inverse proportion to their speeds of migration is offset by the electrostrictioti. Wagner8 has pointed out that Euler's theory is untenable, since the viscosity of the solvent may be diminished by solutes which art: iionelectrolytes. As :L possible explanation of the phenomenon, Wagner suggests that the amount of solvent in a given space is diminished by the solute and that this leads to a lowering of the viscosity. If the solute have a high viscosity, then tlic viscosity of the solution will he greater than that of the solvent. Iiankcn anti 'I'aylor10 have pointed out that a t 8 ' urea diminishes thtviscosity of water, but as the temperature is raised the viscosity of t h e solution becomes greater than that of the solvent. Recently the author" deterrniiied the viscosities of several solutions of potassium salts having lower viscosities than that of the'slovent. 'fhe determinations were extended from dilute to concentrated solutions and it was found that in every case the viscosity-concentration curves passed through a minimum. 'I'he suggestion was put forward that the abnormal behavior of the potassium salts resulted from the combined action of the ions and the undisIvied. Ann., 20, 2 5 7 . Z. pltysik. C h e m . , 5 , 31. Ibid.,
' Ibid.,
I,
285.
336. Il'ied. Ann., 43, 15. Trans. Roy. SOC.,Edinburgh, 45, 397. Z . physik. C h e m . , 25, 536. a Ibid., 15, 79. a! Ibid., 46, 867. lo
"
22,
LOC.cit. ,J. c h i m . phys., 5 , 344.
NEGATIVE VISCOSITY.
723
sociated molecule. The potassium ion appearing to lower the viscosity of the solvent, while the different anions and the undissociated molecules tended t o increase it. Shortly aiter this paper was written Jones and Veazey‘ suggested a possillle explanation of negative viscosity. In the course of their investigations the anomalous behavior of potassium thiocyanate directed their attention t o this phenomenon and they found that the solutes which diminish the viscosity of water are those whose cathions have large atomic volumes. If the ions of the solute are large, relative to the molecules of the solvent, then the effect of the dissolved salt will be t o reduce the viscosity of the solvent. In view of what has been done in this field it has seemed of sufficient importance t o extend my work and include other saline, aqueous solutions exhibiting negative viscosity. The salts chosen for more careful study were ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, and rubidium iodide.
Apparatus and Method, The method of measuring the viscosities was the well-known transpiration method of Poiseuille-Ostwald. The viscometers were placed in a bath of water maintained a t constant temperature and the times of transpiration were measured with a stop-watch which had been carefully compared with a n accurate chronometer. The densities were determined with a pycnometer of the SprejgelOstwald type. The viscometers were frequently cleaned with chromic acid and special precautions were taken t o protect them from dust. The constants of the tubes were frequently checked by measuring the times of transpiration of pure distilled water and solving for k,in the formula
where 7 is the absolute viscosity of water a t a definite temperature, d the density of water a t the same temperature, and t the time of transpiration a s measured by the stop-watch. The values of 71 and d were obtained from the tables of Landolt and Bornstein. The concentration of the solutions was determined either by direct weighing or by analysis. The salts used were obtained from Kahlbaum and were sufficiently pure to warrant using them without recrystallization. a
Am. Chem. J., 37, 405.
724
FREDERICK 11. (;I.:TMAN.
Results, In the tabulation of results the symbols have the following significance : nz = concentration of solution in gram-molecules per liter. tl = density of solution referred to water at 4 O C. 7 = viscosity in C. G. S . units (dynes per square centimeter). TABLEI. NH,Cl-z d.
jo. 7.
o 00889
.ov;1
I
1.0138
0
00S8~
1.0204
0
ooxs2
1.0268
0
008S0
1.0331 I 0.194 1 0 4 9 I .05I h I 0630
0
0os;x
0
008s j
0
008f);. 00()04 00925
'
0 0
TABLE11.' "$1. m.
17 100.
0.68
0,0128
0.0080
I .62
0.0123
0.0081
2.93 4.lAh'.
among whom ma!- lie tiicntiollrd Arrhcnius,' Hulcr,? Sti-iiidherx,J :md Holland.' In 1896 Moore,' in im iii\vstiption of tlic viscosities of some salt solutions, attempted to find somc relation b c t r v v c ~viscosity ~ and ronductivity, hut witliout inuch siicccss. Hc nxtkrs tllc sig-nifiraiit rtvi:irk
m. Fig. 6 .
that "more extended observations must lw iii:uIr I I ~ O I I IIic rchtiou or viscosity and condiictivit?-, pcrlialis C V ~ I Isome 1 1 w tnctl~odof r o m p u i . son arrived a t , Ixforr tlir two subjccts :m lilnccd in tlicir riglit rehtioii." The recent work of Bousfield and 1,owry' 1i;is Ird to tlic foriiiril:r
connecting conductivity and tenipuatiirc, thr Imwntliesis 1)viily Slot ((1's expression for the changc in viscosity with teiiqxrxtiirr.
' 2.physzk. Chem.. 9, 487. Ibid., 35, 536. Ibid., 14, Z Z I . ' Wied. Ann., 50, 261. Phys. Rev.,3, 321. 8 PVOC. R ~SOC., ~ 74, . *no.
'
735
X\TEGATIVE VISCOSITY.
I t scenird of iiitcrcst to coiiipm tlic \-iscositics of tlir normal solutiotis with their coiiducti\-ities as given by Kohlrausch,' making use of Wirdcmaiin's relation.
t.
Fig. 7.
'l'hc results dnctivity.
:ire
givcii iti Tatilc S S I I I , 2 cleiiotiiig the rquivalent conTABL13
,~
lernp.
.I.
NaCl . . . . . . . . . . . . . . . . . . o.0116 N'aUr . . . . . . . . . . . . . . . . . . o . a r i g . . . . . . . . . . . . . O.OLI4 KCI . . . . . . . . . . . . . . . . . . . o.oro.5
XXIII. = 1x0.
h
74.4 70.5 66.0 98.2
. . . . . . . . . . . . . 0.0103 . . . . . . . . . . . . . o.omr
103.7 103.4
KNO, . . . . . . . . . . . . . . . . . o.oro4
80.4 97.0 ro2 .9
NH,Br ......... . . . . . . . .
o.0101
1o4.o
NH,NO, . . . . . . . . . . . . . . . o.om1
' Das LeituerMgen der Elekfvolyte.
8X.q
+. n.863 0.81, 0.752
1.03' I ,069 r.041
0.839 0,999 1.039 1.016 0.g01
736
PRIIDEKICK 1.1. GGThIAN.
The values of T$ for the halogen salts of potassium and ammonium are nearly constant, the average value being 1 . 0 3 2 . I t is evident, however, that some other factor besides those given is required t o establish the relation between viscosity and conductivity. Discussion of Results. A survey of the results obtained with the potassium, ammonium and rubidium salts examined seems t o confirm the theory suggested by the author, that the phenomenon of negative viscosity is due to a tendency of the cathions to lower the viscosity of the solvent while the anions and the undissociated molecule tend to increase it. Jones and Veazey' have called attention to the fact that those salts whose cathions have the greatest atomic volumes exhibit negative viscosity when dissolved, provided the atomic volumes of the anions are not so small as t o counteract the effect of the catliions. In terms of their theory we should expect, for a series of salts having the Same anion, that the lowering of the viscosity would vary directly with the atomic volume of tlic cathion. 'I'hese authors have showii this to be approximately t r u e for the notmal solutions of the chlorides of potassium, rubidium and caesium. From Figs. I and 2 we find that rubidiuni iodide lowers the viscosity t o a greater extent than potassium iodide while the lowering produced by ammonium iodide is slightly less than that proclucctl by rubidiuni iodide. Owing to scarcity of material it was impossible to extend the measurements on rubidium iodide to more coriceritrateti solutions. Differences in the degree of dissociation a t different temperatures cannot be employed to explain t h e greater negative viscosity observed in each case for the lower tcniperaiires. I t is probable that the lower temperatures favor the formation of molecular complexes which, owing to greater \.ohme and smaller surface, tend to diminish the \.iseosit!.. I h n s t a i i ' has furnished experimental e\-idence for the formation of these complexes, which are stablcs only a t relatively low temperatures. By means of this supposition it is possible to explain the case of negative viscosity presented b!, urea a t 8' and other instances of negative viscosity observed kvitli solutiolis of nori-electrolytes. ,, 1 he empirical formula or Slotte for calculating viscosities a t various temperatures is found to apply t o thc, solutions studied between 1 5 ' and 20°.
Assuming with Wiedemdnri that the migration velocity varies invxsely with the viscosity for a fixed potential gradient, the product of 1 I'
Jones a n d l ~ e a z e y ,LOG.cit. J . C'lictn. Soc., 85, S I j ; %. p h y s i k . C h c m . , 49, 590
ANHYDROUS CHLORIDES ON TELLURIUM.
737
the viscosity and conductivity should give a constant. I t has been found that this relation is only approximately true for the solutions investigated. COLUMBIA UNIVERSITY,
March, I@.
THE ACTION OF VARIOUS ANHYDROUS CHLORIDES ON TELLURIUM AND ON TELLURIUM DIOXIDE. BY VICTOR LENEER. Received February 25, 1908.
In an earlier paper' the action of sulphur monochloride on elementary tellurium has been shown to result in the production of tellurium tetrachloride and sulphur, when the sulphur monochloride is in excess, while Krafft and Steiner,? in studying this reaction, observed that when an excess of tellurium is heated with sulphur monochloride, tellurium dichloride results. Further study on the action of tellurium and the dioxide with active reagents has shown that with many of the anhydrous chlorides, especially with those which are liquid a t the ordinary temperature, tellurium tetrachloride is produced. In certain cases the tetrachloride immediately separates from the solution in pure form while with a number of reagents of this character actual union takes place and a crystalline condensation product separates. Tellurium Dioxide and Sulphur Monochloride.-Tellurium dioxide, when treated with an excess of sulphur monochloride, is transformed into the tetrachloride, sulphur dioxide being formed a t the same time, according to the equation : TeO, 2S,Cl, = TeCl, SO, 3 s .
+
+ +
Analysis, TeCl,: Calculated, C1, 52. 79; Te, 47.21. Found, C1, 52 0 7 ; Te, 46.65.
When, on the other hand, an excess of tellurium dioxide is heated with sulphur monochloride, the reducing action of this reagent steps in and the result is that the dichloride of tellurium is formed, thus: TeO, S,Cl, = TeCl, S SO,. The formation of tellurium tetrachloride by the action of excess of sulphur monochloride on tellurium dioxide takes place readily ; the reaction can be materially hastened by warming, and under these conditions, preparation of a large amount of the tetrachloride can be accomplished in a very short time. Extraction of the salt with carbon bisulphide is advisable in order t o remove an excess of sulphur. Behavior of the Oxyclzlorides 01 Sulphur toward Telluriuma and Telluriuin
+
* THISJOURNAL, a
Ber., 34, 560.
24, 188.
+ +
