NOTES
504
capillary rise in the Scarpa viscometer. The equation y =
1/2rhg(dl
- d,)
(1)
where y is the surface tension, T the radius, h the capillary rise, g the acceleration due to gravity and dl and d, are the densities of the liquid and vapor, respectively, was used for the calculation. The viscosity data obtained are listed in Table I. TABLE I VISCOSITY OF PERCHLORYL FLUORIDE t,
OC.
cent $oise
-76.5 -75.0 -65.9 29.9 53.8
0.572 ,563 ,500 .173 .I42
Dev. obsd. - calcd.
-0.010 - .004 ,013 ,003 - ,002
+ +
These data are fitted by the linear formula 299 log q (centipoise) = -
(2) T - 1.755 Deviations between the observed values and those calculated using equation 2 are shown in column three of Table I. The surface tension data are listed in Table 11.
TABLE I1 SURFACE TENSION OF PERCHLORYL FLUORIDE oc. -75.2 -65.8 -55.6 t,
Surface tension (dynes/cm.)
Vol. 61
Calculation of Constants.-According to Bjerthe dissociation or ((hydrolysis" constants of a polyethyleneamine, in this case tetren, can be determined from the equilibria which are present in an aqueous solution [tetren H p + ] _I [tetren Hd4+] H +
+
[tetren H44+][H+] [tetren HK6+] [tetren H4"] I _ [tetren Ha*+] H + [tetren Has+][H+l Kz [tetren Hd4+] [tetren H33+] [tetren Hz2+] H + [tetren H?+] [ H + ] IC3 = [tetren HaS+] [tetren H?+] I _ [tetren H + ] H + [tetren H+][H+I K4 = [tetren H 2 + ] [tetren H + ] [tetren] H + K 5 = [tetren][H+I [tetren H + ]
K, =
+
+
Z
+
Z
L
+
--
These five constants can be calculated from pH measurements of solutions containing known concentrations of the amine and an inorganic acid. Using Bjerrum's method the following equations can be derived where fi = the mean number of hydrogen ions attached to the amine molecule. P K I = PH
n-4 + log [rn]
24.1 22.3 21.3
(6)
(7)
The estimated uncertainty in the viscosity and surface tension data is &2%, Temperature measurements were made with calibrated thermocouples and were known to h0.1". Acknowledgment.-The writers wish to express their appreciation to Mr. W. J. Barry, of The Pennsylvania Salt Manufacturing Company, for performing the high temperature measurements.
(9)
Experimental The technical grade amine purchased from Carbide and DISSOCIATION CONSTANTS OF Carbon Chemicals was redistilled in vacuo. The tetren distilled a t 169-171' under pressure of 0.05 mm. However, as POLI'ETHYLENEAMINES. 11. THE indicated by potentiometric titration with a standard acid DISSOCIATION CONSTANTS OF solution, distillation alone did not purify the amine sufficiently, and several other methods were used to prepare pure TETRAETHnENEPENTAMINE amine salts. I. Purification of Tetren by Precipitation of the Penta BY HANS B. JONASSEN, FREDW. FREYA N D ANNEKE 150 Acid Salts. a. Tetren Pentahydroch1oride.-About SCHAAFSMA g. of the distilled amine was dissolved in 300 ml. of 95% Contribution f r o m the Richardson Chemistry Laboratory, Tulane ethanol and the solution cooled to 10' in an ice-bath. One University, New Orleans, Louiaiana hundred eighty ml. of concentrated HC1 was added dropwise Received October 10, 1968 so that the temperature of the solution did not exceed 20'. A white precipitate appeared during addition of the last 30 The dissociatioii constants of the three lower ml. The precipitate was filtered, recrystaljized three times members of this polyethyleneamine series, as well as from ethanol and water, and washed with ether after the their complexity constants with various metal ions, last recrystallization. The precipitate was dried by SUChave been determined previously by several inves- tion. A weighed sample of the precipitate was titrated tigators. tiometrically with standard sodium hydroxide so This paper reports methods of purification of 0.1114 g. of the precipitate required 6.00 ml. of 0.2318 M tetren and the determination of its acid base con- NaOH for neutralization, indicating that the salt formed 1s the pentahydrochloride. stants. (1) Abstracted from the Doctoral Dissertations of F. Frey, June, 1954, A . Schaafsma, June, 1955, Tulane University, New Orleans, Louisiana.
(2) J. Bjerrum, "Metal Amine Formation in Aqueous Solution, Theory of the Reversible Step Reaction," P. Haase and Son, Copenhagen, 1941.
NOTES
April, 1957 The precipitate was also analyzed for chloride by titration with AgN03using thiocyanate as the indicator. Anal. Calcd. for Tetren.5HCl: C1, 47.7. Found: C1, 47.2, 47 .l. The low chloride analysis is due to incomplete drying of the sample. Attempts to obtain a completely dried sample always resulted in partial decomposition of the salt. b. Tetren Pentahydr0nitrate.-About 150 g. of the distilled amine was dissolvedoin 200 ml. of 95% ethanol and the solution cooled to 10 . One hundred ml. of concentrated HN03 was added dropwise so that the temperature did not exceed 20'. The white precipitate was filtered by suction, recrystallized five times from ethanol and water, and washed with alcohol and ether after the last recrystallization. The precipitate was dried by suction. A weighed sample of the salt was titrated potentiometrically with standard sodium hydroxide solution; 0.1289 g. of the salt required 5.20 ml. of 0.2318 M NaOH, indicating that the salt formed is the pentahydronitrate. Paper chromatographic tests on all salt samples indicated the presence of only one component. 11. Preparation of Solution.-The standard aqueous amine solution was prepared by dissolving a weighed amount of the nitrate (chloride) salt. The solution was standardized by potentiometric titration with standard sodium hydroxide solution. This solution was then diluted to give a 0.001 M tetren hydronitrate solution. A carbonate-free sodium hydroxide solution was prepared in the usual manner. After dilution it was standardized by titration with standard acid solution using modified methyl red as the indicator. A 0.05000 M sodium hydroxide solution was then prepared from this stock solution. 111. Determination of Dissociation Constants.-The dissociation constants of the tetren were determined by titrating 50 ml. of 0.001 M solution of the nitrate and chloride salts, with 0.05 M NaOH, ming a Beckman model G pH meter and a Beckman all-purpose glass electrode. The titration was accomplished in a 4-neck flask, three necks symmetrically located around the center neck. The center neck was equipped with a stirring rod for mechanical stirring. The calomel and glass electrodes were placed in two of the other necks. The sodium hydroxide was introduced from a 10-ml. buret into the fourth neck. Nitrogen was bubbled through this neck during the titration. The titrations were made at 25 f 0.1', 35 f 0.1' and 45 f 0.1". The p H meter was standardized a t each temperature Kith Beckman buffer solutions.
Discussion It was found that pK1 could not be calculated from the titration data as these concentrations did not make ft large enough. A separate titration was therefore performed in which the solution was made 0.005 M with HN03 and 0.001 M with tetren 5HN03. This solution was then titrated with 0.05 M NaOH. A similar method was used for the chloride salt. pK1 could also be calculated only a t 25", as the accuracy of the pH meter did not permit any calculations a t 35 and 45" because of the correction for [H+]which must be applied to C,. Table I lists the value calculated for one of the five constants of tetren from the experiment data. e
TABLE I DETERMINATION OF pK6 DISSOCIATION CONSTANTSOF TETREN AT 25' log
ctatren
0.0009183 .0009166 ,0009149 .0000132 .0009116
Cs
G.
pH
n __ 1 -?I
Ad
pKs
5723 0.62 9.81 $0.21 0.02 9.98 .54 9.89 4933 .07 .02 9.94 4218 .46 9.99 .05 .02 9.92 3534 .39 10.08 - .20 .01 9 . 8 7 2871 .32 10.16 - .32 .01 9.83 9.92
+ -
505
Where Ctetren = total concentration of tetren in solution C. = [tetren H + ] + 2[tetren H 2 + ] + 3[tetren H?+J
+ 4[tetren H4"+1 + 5[tetren Hb6+]
Table I1 lists the values determined for the five constants a t the three temperatures. TABLE I1 DISSOCIATION CONSTANTS AT 35 AND 45' 25'
PIG PK2 PKa PK4 PKb
2.65 4.25 7.87 9.08 9.92
350
450
2.43 3.99 7.54 8.81 9.65
3.74 7.26 8.53 9.38
Further thermodynamic data calculated from them have no more accuracy than that to which the change in pK with temperature is shown; they are therefore not reported. The values so calculated, however, are in line with those expected from a comparison with the lower polyamines. Acknowledgment.-The financial help of the Office of Ordnance Research, U. S. Army, is gratefully acknowledged in this and continuing investigations.
THE DIFFERENTIAL THERMAL ANALYSIS O F PERCHLORATES BY MEYERMELVINMARKOWITZ Department of Chemical Engdneering New York University, Uniuersit?l Heights, New Y d ~ kCity, N . Y . Received November 10, 1068
The significance of differential thermal analysis (DTA) curves may often be increased when taken in conjunction with other studies. By supplementing observed DTA curves with information derived from chemical and X-ray analyses, kinetic mechanismslJ and phase diagrams3t4 have been determined. In a recent paper on DTA by Gordon and Campbel1,s the consistent presence of an exothermic break in the DTA curves of the perchlorates of silver, the alkali metals and the alkaline earths is quite puzzling. Except with such substances as the hydrazine and ammonium nitrates and perchlorates which undergo vigorous oxidation reactions, and various azides, it is to be anticipated that the thermal decompositions of most inorganic materials which yield, a t least in part, gaseous products are endothermic. From results reported in the literature concerning the pyrolysis of potassium perchlorate, it is believed that the endothermic nature of the decomposition of this salt can be adduced and that the general exothermic phenomena observed for the perchlorates6 can be traced t o the occurrence of reaction product crystallization. It has been noted that in the heating of potassium perchlorate, there is a t first the appearance of a (1) R . K. Osterheld and L. F. Audrieth, THISJOURNAL, 86, 38 (1952). (2) R. K. Osterheld and M. M. Markowitz, ibid., 60, 863 (1956). (3) R. K . Osterheld and R. P. Langguth, ibid., 69, 76 (1955). (4) E. P. Partridge, V. Hioks and G. W. Smith, J . A m . Chem. Soc., 68, 454 (1941). (5) S. Gordon and C. Campbell, Anal. Chem., 27, 1102 (1955).
