LEROY D. JOHNSON .
. . .
.,
Storer College, Harper's Ferry, West Virginia E
THIS JOURNAL has published .,several illustrating the r81e of catalysts inorganic and inorganic 'oxidations. The method submitted is a simple procedure based on the catalytic decomposition of hydrogen peroxide by manganese dioxide and the suhsequent oxiddtion of methyl alcohol to formaldehyde. The equations: 2HrG --P 2CHsOH
2HsO
f Or
+ OI +2HCHO + 2 H z 0
The usual laboratory method of illustrating this oxidation is by using a heated copper spiral as a catalyst and plunging the same into a test-tube or graduate containing a few cc. of methyl alcohol. The odor of formaldehyde is then noticed. The second procedure is presented as a supplement to the usual method because for the performance the time limit is reduced to a minimum and the materials and
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' H a m , J. CHEM.Eouc.,11, 575 (1934).
a JOKNSON, ibid.,
16, 238 (1939).
..
apparatus employed are usually available in the ordinary laboratory. The method employed is as follows. An eight-inch hard glass or pyrex glass test-tube is placed upright in a ring stand and clamped. The bottom of this tube is covered with a oue-eight inch layer of manganese dioxide and heated gently with an ordinary Bunsen burner. Ten cc. of freshly prepared or C.P. methyl alcohol is mixed with fifteen cc. of three per cent. hydrogen peroxide solution. After shaking this latter mixture thoroughly and turning off the Bunsen burner the alcohol-peroxide mixture is added drop by drop by means of a pipet to the eight-inch test-tuhe. As soon as a few drops of the alcohol-peroxide mixture strikes the heated manganese dioxide a vigorous reaction takes place, causing a glowing of the dioxide. There immediately is produced the sharp odor of formaldehyde which is made more perceptible by fanning the fumes toward the investigator's nose in the usual fashion.
To con6rm the aldehyde, however--although the passed through a filter paper into a clean test-tube. odor is sharp enough, the remainder of the alcohol- A few cc. of this clear solution suspected of containing peroxide may be slowly added until finally all the mix- the aldehyde are added to ammoniacal silver nitrate tnre is added and the vigorous action ceases. Then, (Tollen's reagent). Upon gentle heating the separathe mixture of manganese dioxide, water solution of tion of metallic silver takes place-a confirmatory test formaldehyde, and any unchanged methyl alcohol is for the aldehyde.
