Methyl alcohol, determination

To the product from Step 1 (0.118 mol) at 10 °C was added 98% H2SO4 (0.2 g) dropwise so that the temperature remained below 28 °C. After the exotherm had subsided, the mixture was stirred 7 hours at 25 °C resulting in a slightly viscous solution. Titration with BU4NOH in methyl alcohol determined the oligomer had a molecular weight of 450 AMU. 

An important application of the critical solution temperature is to the determination of the water content in such substances as methyl and ethyl alcohols. Here the system is usually the alcohol and a hydro carbon, such as -hexane or dicyclohexyl the water is, of course, insoluble in the hydrocarbon. Thus, the methyl alcohol - cyclohexane system has a C.S.T. of 45 -5° and even 0 01 per cent, of water produces a rise of 0-15° in the C.S.T. The experimental details are given below. 

Conversion of (3- into a-glucose penta-acetate. Add 0-5 g. of anhydrous zinc chloride rapidly to 25 ml. of acetic anhydride in a 200 ml. round-bottomed flask, attach a reflux condenser, and heat on a boiling water bath for 5-10 minutes to dissolve the solid. Then add 5 g. of the pure P glucose penta-acetate, and heat on a water bath for 30 minutes. Pour the hot solution into 250 ml. of ice water, and stir vigorously in order to induce crystaUisation of the oily drops. Filter the solid at the pump, wash with cold water, and recrystaUise from methylated spirit or from methyl alcohol. Pure a-glucose penta-acetate, m.p. 110-111°, will be obtained. Confirm its identity by a mixed m.p. determination. 

Technical formalin contains 8-10 per cent of methyl alcohol, so that it is not possible to use the table of densities (Note i of the preparation) for determining the formaldehyde content of the solutions. For example, a solution containing 37 per cent of formaldehyde and 10 per cent of methyl alcohol would have a density of 1.09 and correspond to 28 per cent of formaldehyde in pure water. In view of this, the recorded yield should probably be 64-66 per cent instead of 86-89 cent. 

Typical normal-phase operations involved combinations of alcohols and hexane or heptane. In many cases, the addition of small amounts (< 0.1 %) of acid and/or base is necessary to improve peak efficiency and selectivity. Usually, the concentration of polar solvents such as alcohol determines the retention and selectivity (Fig. 2-18). Since flow rate has no impact on selectivity (see Fig. 2-11), the most productive flow rate was determined to be 2 mL miiT. Ethanol normally gives the best efficiency and resolution with reasonable back-pressures. It has been reported that halogenated solvents have also been used successfully on these stationary phases as well as acetonitrile, dioxane and methyl tert-butyl ether, or combinations of the these. The optimization parameters under three different mobile phase modes on glycopeptide CSPs are summarized in Table 2-7. 

A From Table 13-1 we know that AHvap = 38.0 kJ / mol for methyl alcohol. We now can use the Clausius-Clapeyron equation to determine the vapor pressure at 25.0° C = 298.2 K. 

This reagent is very much used and It is best to keep a stock. Dissolve 25 g. of potassium hydroxide sticks in 100 c.c. of methyl alcohol by warming or by leaving over night in the cold potassium hydroxide in ethyl alcohol soon resinifies. Remove carbonate by filtration and determine the KOH content by titration. 

Hydrolyzes in water forming methyl alcohol and hydriodic acid. The estimated half-life in water at 25 °C and pH 7 is 110 d (Mabey and Mill, 1978). At 70 °C, the hydrolysis rate was determined to be 3.2 X 10 Vsec which is equivalent to a half-life of 6 h. (Glows and Wren, 2003). May react with chlorides in seawater to form methyl chloride (Zafiriou, 1975). 

BuOH = butyl alcohol MeOH = methyl alcohol THF = tetrahydrofuran. c Compositional heterogeneity (CH) was determined. d Descending solvent strength with development path. e Two-dimensional development. f Ascending solvent strength with development path. 

Detection and Determination of the Methyl Alcohol.—(A). Qualitative Test, (a) 25 c.c. of the spirit are slowly distilled and the first 3-4 c.c. of distillate mixed in a conical flask with 25 c.c. of water, 15-20 drops of dilute sulphuric acid and 3-4 c.c. of 1% chromic acid solution, and again distilled. The first 5-6 c.c. of distillate are discarded, the next 10 c.c. being treated with 1 c.c. of 4% phenylhydiazine hydrochloride solution, 0-5 c.c. of 4% ferric chloride solution and 2-3 c.c. of concentrated... 

The colorimetric method of determining methyl alcohol in spirit is very rapid and if the conditions are faithfully adhered to, also very exact. It is especially advantageous when the methyl alcohol is present in small amount (up to 5-6%). When, however, the methyl alcohol occurs in larger proportions, the gravimetric method is to be preferred (see p. 258). 

Methyl alcohol, besides occurring in spirits derived from denatured alcohol—in which case the methods of detection and determination have already been indicated (see p. 254)—may also be found in larger quantities, especially in alcoholic beverages, liqueurs, etc., to which it is added fraudulently in place of ethyl alcohol. In the latter case its detection and determination require the previous elimination of extraneous fixed and volatile substances. 

Quantitative Determination.—1. Colorimetric Method. This is recommended especially with small proportions of methyl alcohol (up to 5-6%). To 20 c.c. of the distillate (corresponding with 10 c.c. of the original spirit), in a 100 c.c. measuring flask, is added sufficient ethyl alcohol, free from methyl alcohol, to give 9 c.c. of total alcohols in the liquid when diluted to 100 c.c. the liquid is then made up to volume with water. The colorimetric determination of the methyl alcohol is carried out on 1 c.c. of this alcoholic solution according to the instructions given on p. 255. 

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