Quanitative Colorimetric Microdetermination of Methanol with Chromotropic Acid Reagent

Abstract

964together through the 3-way stopcock. If the copper block is a t room temperature, the meniscus will fall in the right leg and rise --in the leftleg. ' The copper block is then cooled by direct immersion in liquid air until the meniscus in the right leg is back to a Dosition near the upper tungsten contact. Theliquild air is remdved, a glass test tube slipped over the copper block, and the test tube immersed in liquid air. The position of the mercury in the manometer then turns the heater current off and on, so as to maintain the meniscus near the contact point. The rheostat in the heater circuit and the depth of the liquid air around the test tube are adjusted so that the off and on periods for the heater are approximately equal in duration. Whe: roperly adjusted the temperature remains constant to *0.3 8When it is desired to increase the temperature of the distil1in.g tube to the next value, the height of the mercury in the left leg is reset to the proper position with the mercury in the right leg still a t the tungsten contact. Without further attention the tpmperature quickly rises to the desired value and then is automatically maintained constant at this point. DISCUSSIONThis control unit has been found to be a very satisfactory means of both adjusting and controlling the temperature required for isothermal distillations at low temperatures. The operation of the thermometer is very simple and it requires a minimum of attention from the operator. The apparatus should also be applicable to the control of low temperatures as required in other problems. A N A L Y T I C A L C H E M I S T R YFor use as both a method of temperature measurement and temperature control the 120" type 3-way stopcock in the man. ometer should probably be replaced with a T-type stopcock. This type of stopcock has an advantage when measuring temperatures, as it permits adding mercury to both legs of the manometer simultaneously until the meniscus in the right leg just touches thP contact point. However, when the main application is the presetting of the control point at some particular temperature and the control of the temperature at this point, the 120" type s t o p cock is believed to be preferable. Although the location of the stopcock above the bottom of the manometer makes somewhat inconvenient the removal of all the mercury as required when filling the thermometer with helium, it has the advantage of permitting relubrication of this stopcock without loss of the helium from the reservoir..4 rapid, accurate, and specific method for the quantitative determination of methanol is described in which the methanol is oxidized to formaldehyde and the latter measured colorimetrically with chromotropic acid. The method permits the determination of methanol with a relative error of <2'3&.OBMALDEHYDE when heated with chromotropic acid F (1,8-dihydroxynaphthalene-3,6-disulfonic acid) in the presence of sulfuric acid gives rise to an intense violet-red color (1, 2, 4). The formation of this color is the basis for the analytical method for me...

The Reduction of Formaldehyde by Bacterial Cells

“…Two methods were employed for measuring small amounts of methyl alcohol Reaction mixtures from which all HCHO had disappeared were treated with K1VInOt in accordance with the procedure outlined by Boos (1948). The chromotropic acid 573…”

“…was diluted to the desired concentration with distilled water. The quantitative determination of I-ICHO was carried out with chromotropic acid reagent, as previously described (Kopper, 1950).Two methods were employed for measuring small amounts of methyl alcohol Reaction mixtures from which all HCHO had disappeared were treated with K1VInOt in accordance with the procedure outlined by Boos (1948). The chromotropic acid 573…”

The Photooxidation of Azomethane. Iii

“…Azomethane was reinoved on a streain of nitrogen as before; 400 mg chroinotropic acid, disodiuln salt, and 0.5 n~l concentrated 1-12S04 were added and a 3-in1 fraction, containing all the methanol (as shown by calibration experiments), was transferred by distillation to a second reaction flask. Methanol was oxidized by potassium perinanganate and the resulting formaldehyde determined with chromotropic acid as described above (9). A set of similarly treated inethanol standards was used to construct the calibration curve of extinction vs. amount of methanol.…”

“…If such is indeed the case then methanol could arise in reaction [2], with R the C H 3 0 radical, and possibly in [9] as well.…”

Pectin Esterase in Relation to Leaf Abscission in Coleus and Phaseolus

“…The pectin was estimiated to be 50 to 60 % esterified (methyl groups were 3.9 % of the dry weight) by the method of Boos (4).…”