260
ROBERT LIVINGSTON SUMMARY
1. The number of structural isomers possible for substitutions of the type X, is given for a simple ring of n members by equation 3 if m 6 3. If m 3 4, equat,ion 3 also holds provided that n - m 6 3. Otherwise additional tcrms must be added. 2. The number of structural isomers possible for substitutions of the type X!,-kX2X3. . . Xk+' is given by equation 16 if k > (2 - e(.)), where e ( n ) = 1 if n is odd and e(n) = 0 if n is even. If IC = 2, the number of isomers is given by equation 15. If IC = 1, the number of isomers is given by equation 14. Equation 8 is a special case of equation 16 and applies to compounds in which all substituents are different (rn - 12 = I ) , provided that m > (2 - e(n)). Equation 9 applies to the case m = 2. 3. A general discussion, covering all possible substitutions into a simple symmetrical ring and using the preRent method of generalizing both the ring and the degree of substitution, will be given in a subsequent paper. REFERENCES (1) POLYA, G . ~ I I ~Chim. v . Acta 19, 22 (1036); Z. Krist.
93, 415 (1036); Compt. rend. 201,
1167 (1935). (2) HILI,,T. L.: J . Chem. Phys. (in press).
T H E RATE OF DECOMPOSITION OF HYDROGEN PEROXIDE IN CONCENTRATED SO1,Ul'IONS ROBERT LIVINGSTOS' School of Chemistry, Iiistitute of Technology, University of Minnesota, dlinneapolis, dlinnesola Received December 18, 1042
With few exceptions (2) studies of the rate of decomposition of hydrogen peroxide have been confined to dilute solutions. In the present experiments the rate of deromposition of concentratcd hydrogen peroxide (80 to 83 pcr cent) in Pyrex, wax-lined, lacyut~ed,and tin vessels was measured at 25°C:. and 35.7"C. The effects of 2 per cent sulfuric acid and of tin, in the form of metastannic acid, upon the rate were determined. MATERIALS, APPARATUS, AND PROCEDURE
The sample of S3 per cent' hydrogen peroxide was prepared from perhydrol (30 per cent hydrogen peroxide containing 0.1 per cent sulfuric acid as a preservative) by a combination of flash and fractional dist,illation in an all-Pyrex still a t 1
Present address: Dtrpartmerit of Clicmistry, University of Chicago, Chicago, Illinois.
26 1
DECOMPOSITION OF HYDROQEN PEROXIDE
a pressure of about 20 mm. (3). A few experiments were performed with a sample which had been “freed from dust” by the usual procedure of distillation a t low temperature (approx. 10°C.) and pressure (less than 1 mm.). In this distillation, the receiver was rinsed by pouring the distillate back into the distilling pot and then repeating the distillation. All glassware was cleaned by treatment with cold chromic-sulfuric acid for several hours, followed by careful rinsing, and finally by steaming for at least 1 hr. The rate was measured manometrically, using a modified Warburg apparatus (1). The peroxide samples (1.OO cc.) were contained in small Pyrex cylinders of 3.5-cc. capacity, which were closed except for a small hole in the side, near the TABLE 1 Sumniary of esperimental resulls DATE OF EXPERIMENT
April 16-20.. . . . . .
CONDITIONS
RATE A I 25°C. .IMOLES PER LITE€ PER SECOND
BEAT OF ALTIVATION N CALORIES PER MOLE
6.1 4.7
x
10-7
19, loo 20,700
4.0 2.6
x 10-7
18,800 16,000
Original solution in glyptal A second sample of the solution in the Sam glyptal vessel
8.7 5.6
x 10-7 10-7
19,500 17,600
May 13-15. . . . . . . , Original solution plus 2 per cent sulfuric acid in Pyrex May 17-20., ... , . . . Solution, which had heen “freed frcmni dust” on May 7, in Pyrex
3.1
x 10-7
16,100
4.6
x
10-7
17,800
Way 20-26. . , . . , . . Original solution plus motastanuic arid (suspension) in Pyrex Original solution in tin vessel
2.7
x
10-7
15,800
x
10-7
15,500
Original (83%) solution in Pyrex Original solution in Pyrex
.
April 23-25., , . , . Original solution in Pyrex May 9-13, . . . , , , . . Solution, “freed from dust” on M
