Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/206

Rh 196 A tribasic acid forms two methyl acids and one neutral ether ; we have, for instance, (5) (From P0 4 H 3 ); P0 4 (CH 3 )H 2 ; P0 4 (CH 3 ) 2 H ; P0 4 (CH 3 ) 3. It would, however, be a great mistake to suppose that whether, for instance (Ex. 3 and 4), the monomethyl or the dimethyl compound is formed depends on the quantity of methyl-alcohol employed per unit of acid. This depends far more largely on other conditions, as will be illustrated in next paragraph. The methyl-salts of oxygen acids are called esters, in opposition to the chloride, bromide, iodide, sulphide, and oxide, which are set apart as ethers. Broadly speaking, ethers are not, while esters are, readily decom posed by water into their cogeners; but the nitrate CH 3. NO 3 behaves in this respect like an ether. Action with Sulphuric Acid. Methyl-alcohol mixes with oil of vitriol with considerable evolution of heat and (always only partial) conversion of the two ingredients into methyl- sulphuric acid. Equal volumes of acid and alcohol give a good yield. To prepare pure methyl sulphates, dilute the mixture largely with water, avoiding elevation of temperature (which would regenerate the ingredients), and saturate with carbonate of baryta. Filter off the sulphate of baryta to obtain a solution of the pure methyl sulphate S0 4. CH 3. ba (where ba = ^Ba = 1 eq. from which this salt is easily obtained in crystals. From the baryta salt any other methyl sulphate is readily obtained by double decomposition with a solution of the respective sulphate ; the acid itself, for instance, by means of sulphuric acid. At higher temperatures the reaction between vitriol and methyl-alcohol results in the formation of methyl-ether, (CH 3 ) 2 O, or of normal sulphate of methyl, (CH 3 ) 2 SO 4 . The ether is a gas condensable into a liquid which, under pressure of one atmosphere, boils at 21 C. The gas dissolves in about one thirty-seventh of its volume of water ; far more largely in alcohol and in ether; most abundantly in oil of vitriol, which dissolves about six hundred times its volume of methyl-ether gas, thus affording a very handy means for storing up the gas for use. The solution needs only be diluted with its own volume of water to be broken up into its components (Erlenmeyer). Liquefied oxide of methyl is now being produced on the manufacturing scale, and sold as a powerful refrigerating agent. One part of sulphuric acid is mixed with a little over one part of dehydrated wood-spirit, and the mixture heated to 125 to 128 C. (130 being carefully avoided), when methyl-ether goes off. When the mixture is exhausted, more wood-spirit is added to the residue so as to re-establish the original specific gravity (of 1 29), and the heating resumed, which again furnishes a supply of the gas, and so on. This proves that the process is not, as used to be supposed, one of mere dehydration, but a cycle of reactions analogous to those in the ordinary process of etherification, as shown by the equations : (1 ) S0 4 H 2 + CH 3 OH = S0 4. HCH 3 + H 2. (2) S0 4. H.CH 3 +H. 0. CH 3 = S0 4 HH + CH 3 .O.CH 3. The ester, S0 4 (CH 3 ), though obtainable by distillation of the alcohol with 10 parts of vitriol, is more conveniently prepared from pure methyl-sulphuric acid by distillation in vacuum at 130-140 C ; thus : -2S0 4 CH 3. H = S0 4 H 2 + S0 4 (CH :i ) 2. It is a colourless liquid, smelling like peppermint, specific gravity 1 327 at 18; it boils at 187 to 188 C. Chloride of methyl, CH 3 C1, readily produced by the action of hydrochloric acid gas and hot methyl-alcohol (preferably in the presence of chloride of zinc as an auxiliary dehy- drator), is a gas which, under ordinary pressure, condenses into a liquid at - 23 C. The gas, at ordinary temperatures (though very readily soluble in alcohol), is only sparingly absorbed by water, which, however, at 6 unites with it into a solid hydrate. Condensed methyl chloride has become an article of commerce, being largely produced from trimethylamine (vide infra) and used as a powerful frigorific agent, as well as for the extraction of perfumes from flowers. Regarding nitrite of methyl, NO O CH 3 , its interesting isomeride nitromethane, O 2 N CH 3, and nitrate of methyl, NO 3 CH 3, we must refer to the hand books of organic chemistry. Iodide of methyl, CH 3, is obtained by distilling methyl- alcohol with hydriodic acid, which latter is best produced off-hand by addition to the alcohol of iodine and amorphous phosphorus. It is a colourless liquid of 2 269 specific gravity, boiling at 42 5 C., insoluble in water. Organic Methyl-Esters. The more volatile ones are in general easily obtained by distillation of the respective acid with methyl-alcohol, or with methyl-alcohol and oil of vitriol (virtually SO 4 . H . CH 3 ) ; the less volatile ones more conveniently by passing hydrochloric acid gas into a methyl-alcoholic solution of the acid. We have no space for the individual substances ; but the salicyiate C 7 H 5 3. CH 3 may just be named as being the principal component of the essential oil of Gaultheria procumbens (winter green oil). Methylamines. The general result of the action of ammonia on an ester is the formation of alcohol and acid amide. Example (C 2 H 3 0)- O-C Acetate of methyl. . OH + C 2 H 3. NH, With iodide of methyl this reaction is an obvious im possibility ; what really takes place (as A. W. Hofmann has shown for this and all analogous cases) is that the iodide unites with the ammonia into the HI compound HI. NH 2 CH 3 of a base NH 2 CH 3, which can be separated from the acid by distillation with caustic potash, and when thus liberated presents itself as a gas surprisingly similar (almost to identity) to ammonia. The analogy extends to the action on iodide of methyl, which, in the case of rnethyl- amine, NH 9 CH 3, leads to the formation of dimethylamine, NH. (CH 3 ) ; and from the latter again trimethylamine, N(CH 3 ) 3, can be prepared by a simple repetition of the operation. These three amines are closely analogous in their chemical character to ammonia, the points of differ ence becoming the more marked the greater the number of (CH 3 ) s in the molecule. Trimethylamine, having lost all its ammonia-hydrogen, cannot possibly act upon iodide of methyl like its analogues. What it really does is to unite with the iodide into &quot;iodide of tetramethyl-ammonium,&quot; I. N(CH 3 ) 4, analogous to iodide of ammonium, INH 4 , we should say, if it were not the reverse, because the organic iodide (unlike its prototype, which is an ammonium compound only in theory), when treated with moist oxide of silver (virtually with AgOH), really does yield a solution of a true analogue of caustic potash in the shape of hydroxide of tetramethyl-ammonium, N(CH 3 ) 4. OH. In regard to the actual preparation of these several bodies, which is not so simple as might appear from our exposition of their mutual relations, we must refer to the handbooks of organic chemistry. But we must not omit to state that trimethylamine, which only the other day was never seen outside a chemical museum, is now being manufactured on a large scale, and promises to play an important part in industrial chemistry. The waste liquors obtained in the distillation of alcohol from fermented beet root molasses serve as a raw material for its preparation. These liquors, when evaporated to dryness and subjected to dry distillation, yield, besides tar and gases, an aqueous liquid containing large quantities of ammonia, acetonitrile, methyl-alcohol, and trimethylamine. This liquor is neutral ized with sulphuric acid, and distilled, when the nitrile and the methyl-alcohol distil over, to be recovered by proper methods. From the mixed solution of the sulphates of ammonia and trimethylamine the former is separated out as far as possible by crystallization ; the mother-liquor