Vol. 64
DAVIDH. VOLMAX TABLE
LATTICECONSTANTS AXD KAl(SOdv12H:O Temp., O C , a , A.
19.3 1 2 . 1333 19.9 12,1335 2c5.0 12.13313 50, ,5 12.1372 51.1 12. 1.378 52,2 12.1373 ol.lOd = 11.0 * O.:i
1
COEPFICIEh’TP O F E X P A S S I O N O F YI€E
‘e.
T e m p . . “C.
12.2141 12.2112 12,2148 12.2180 13.2181 12.21i9 r r . 1 0 ~= 9.5 * 0.2
a.
NH$Cr(SOd:.12FIrO Temp., ‘ C . a A.
A.
18.8 12.2047 19.0 12.z015 19.1 12. so40 25.0 12.2050 50.6 12.2095 51.1 12.2093 a,106 = 13.1 * 0.3
19.2 19.4 1!>, 6 5(.). 1 50. 8 51.4
ing values of a.106for the first three alums listed above: 3.3, (i.8 and 18.3, respectib-ely. These values are of the right order of magnitude but, otherwise, are in poor agreement with the X-ray values. No data are available for comparison with the result for ammonium chrome alum Potassium chrome alum was also studied a t this same time but the inability, after numerous attempts, to get photographs in the vicinity of 30’ without dehydration led to its abandonment. The authors wish to express their thanks and appreciation to Dr. K. 0. Smith and Professor J. E. Ricci for the sample of thallium alum. They
ALUMSBETWEEN 20-50’
TIAI (SOdz.1 L”rO
1;Hd AI (SOq)?.12 Hi20 Temp, a, A.
22.1 25.0 50.5 51.1
13.2501 12.2510 12.2539 12.2543
a.106 = 10.6
*
0.4
also wish to acknowledge with gratitude a grant from the Graduate School of the University of Minnesota under which this study was carried out. Summary The linear thermal expansion coefficients a for several alums have been measured for the approximate range, 20-50°, by means of X-ray diffraction. The values of (r.106observed are as follows: potassium alum, 11.0 * 0.3; ammonium alum, 9.3 * 0.2; thallium alum, 13.1 * 0.3; and ammonium chrome alum, 10.6 0.4. MINNIAPOLIS, MINNESOTA
RECXIVED APRIL 27, 1942
[CONTRIBUTION FROM THE D I V I S I O X O F CHEMISTRY, COLLEGE O F AGRICULTURE, UNIVERSITY O F CALIFORNIA]
The Vapor Phase Photo Decomposition of Methyl Formate BY DAVID H.
Recently, experiments on the photolysis of methyl formate have been reported by Royal and Rollefson.2 Experiments 011 this same problem had been in progress in this Lsboratory. The results for the photolysis products in this investigation are in substantial agreement iT-ith those giien by Royal and Rollefson. In addition, data on the determination of methanol in the reaction proclucts, and an approximate evaluation of the quantum yield for the reaction were obtained. In a subsequent paper on the photolysis of methyl acetate, Roth and Rollefson3 have given data on the determination of methanol as a photolysis product by oxidizing the alcohol to formaldehyde and treating with Schifi reagent. However, they were unable to analyze for the small amounts of methanol usually obtained iri the decomposition runs, and were forced to obtain (1) On leave of absence. Present address: The Technolngieal Institute, Northwestern University, Evanston, Illinois. (2) Roy31 and Rollefson,T H NJOURNAL, 63, 1521 ilDSI! (3) R o t h and Iiollefson. i b i d . , 64, B Y 0 (1042).
\;OLMAN~
comparatively large amounts of decomposition products by carrying out the reaction in a threeliter bulb. The method given below using a Grignard reagent suflices for the small amounts usually obtained and enables analyses to be made for all of the dccompssition experime!its condxted. Experimental Method The apparatus employed was essentially the same as already reported4 The source of radiation was an Hanovia Alpine mercury lamp. Quan tum yields were determined approximately by using nisnochloroacetic acid as an actinometer in a manner previously described4s5using the reliable value for the hydrolysis quantum yield gh-en by Smith, Leighton and Leighton.‘j Methyl formate was synthesized by allowing formic acid and methanol to react in the presence (4) V o l m s n , ibid., 63, 2000 (1941). (31 N‘ei~monti,Berginann and Hirshberg, ibid.. 68, 1675 (1036). (0) S m i t h . Lciyliton und ].eighton, iDid., 61, 2209 (1939).
Aug,, 1942
THEVAPORPHASE PHOTO DECOMPOSITION OF METHYL FORMATE
1821
TABLEI of hydrochloric acid. The methyl formate was PHOTOLYSIS PRODUCTS AND QUANTUM removed by distillation and washed with concen- METHYLFORMATE YIELDS trated potassium hydroxide. After a second disCO, H1, CHI, COz, CzHs, CHsOH, tillation, the ester was dried over phosphorus % *d % % % % % pentoxide and fractionated. The fraction used 41.3 10.3 5.1 15.0 1.3 27.2 0.7 9.3 5.6 14.9 0.7 29.1 .7 40.5 distilled a t 31.S-32.0'. 9.0 6.0 14.9 1.6 29.5 .8 39.1 After irradiation for definite periods, the gases 7.3 14.4 0.9 29.9 .8 38.2 9.3 non-condensable in a liquid-air trap were collected by means of a Toepler pump and analyzed Discussion by the use of a Blacet-Leighton apparatus for The demonstration that methanol is produced micro gas analysis. The following method was used in analyzing for in the photolysis of methyl formate is evidence methanol. A methyl Grignard reagent in ethyl that ether solution was placed in a trap connected to HCOOCHI +CO CHaOH the photolysis apparatus by means of a stopcock. one of the net reactions postulated by Royal and Prior to an experiment the Grignard reagent was Rollefson,2does occur. thoroughly outgassed and frozen by use of liquid The reaction products were found to be the air. When it was desired to analyze for methanol, same as previously reported.2 The small variathe condensable reaction products plus undecomtion in the mole percentages of the non-condensposed ester were distilled into the trap containing able products from the values given by Royal and the Grignard reagent. Then the mixture was Rollefson may be attributed to the difference in allowed to warm to room temperature and sucexperimental details, especially pressure of methyl cessively frozen and warmed several times. formate and time of illumination. Finally, the non-condensable gas, methane, was The variety of products indicates that the overcollected and determined, both by volumetric all photolysis is complex. However, since @d is measurement and by combustion. less than unity, no appreciable chains are inAn attempt was made to produce hydrogen volved. from methanol by passing the photo-decomposition products over a sodium mirror. However, Summary the results were not reproducible and were con1. The presence of methanol in the photolysis sistently lower than expected or found by the products of methyl formate has been shown. Grignard reagent method. 2 . The decomposition quantum yield for the Complete analytical results and values of decomposition quantum yield, @& are given in the photolysis was found to be approximately 0.75 accompanying table. The pressure of methyl for an ester pressure of 75.0 mm. a t 25". 3. The reaction products were found to have formate was 75.0 mm. in each experiment. Irradiation was for twenty minutes a t 2 5 O , and ap- the following average values: Hz, 9.5%; CO, proximately GOO cu. mm. of gas was collected 40.0%; CH4, 6.0%; COz, 14.8%; C2He, 1.1%; each time. @d is based on the sum of carbon di- CHaOH, 29.0%. RECEIVED M A Y18, 1942 DAVIS,CALIFORNIA oxide and carbon monoxide.
+
