Page:The New International Encyclopædia 1st ed. v. 01.djvu/111

ACETO-ACETIC ESTER. sodium on the ester formed by the union of acetic acid and ordinary alcohol ( i.e.. ethyl acetic ester). Aceto-ucelie ester mixes in all propor- tions with alcohol or with ether, but is only spariiifjly soluble in water. It boils at 180° C. The two hyle of being replaced either by metals or by hydroc.irbon radicles like methyl (CH,), ethyl (C.Hr.), etc., and the substitution products thus obtained J'ield, on treatment with acids and alkalies, a variety of important carbon com- pounds. The ester is, therefore, extensively used for the artificial preparation of various sub- stances fnr scientific purposes.

ACETONE, asV-trm, or DiJirETnyi, Ketone, ClijCOt'Hj. A colorless organic liquid boiling at 5(i'.3 C, and having at 20° a specific grav- ity of U.Tili:. It is volatile and inllamniablc, has a pleasant ethereal odor, dissolves various organ- ic substances such as fats and resins, and mixes in all proportions with water, alcohol, and ether. It is separated from its aqueous solutions by means of calcium chloride. It dissolves con- siderable quantities of acetylene gas (q.v.), and absorbs a very large amount of sulphurous anhydride. It is used as a solvent as well as for the manufacture of chloroform, iodoform, etc. Acetone is produced when various organic substances are subjected to destructive distil- lation: it is thus found in pyroligneous spirit (see Methyl Alcohol) obtained by the dry distillation of wood. It is separated from wood spirit by distilling over calcium chloride. It is usually prepared by distilling barium acetate at a moderate heat, according to the follow- ing chemical equation:

(CH,C00)3a = CAO -i- BaCO, Barium acetate Acetone

The somewhat impure product obtained either from wood spirit or from baiiuiii acetate may be readily ])uritied and dehydrated by the use of the acid sulphite of .sodium, with which it com- bines to form a crystalline solid compound. Pure acetone is obtained from the latter by dis- tilling with sodium carbonate. When acted on by chlorine in the presence of alkali, acetone is converted into chloroform. Iodoform is sim- ilarly produced by the action of iodine (in am- monium iodide solution) and ammonia upon acetone, the reaction forming the most sensitive test for acetone that is known to chemists. When acetone is distilled with strong sulphuric acid, niesitylenc is produced; this reaction has been of great value in determining the chemical con- Btituti(jn of a vast number of benzene derivatives allied to mesitylene. Acetone occurs in small quantities in the blood, and is present in the liquid passing over when urine is distilled. It has Umg been known to chemists as :i product of distillation of acetates^ its composition was first determined by Lieliig and Dumas in 18.32. ACETONES. See Ketones. ACETYL, :'is'e-tTl. An atomic group or radi- cle in organic chemistry. See C.rron ComPOINIIS.

ACET'YLENE (from rwrt,,l). HC=Cn. A colorless gas composed chemically of carbon and hydrogen. It is present in small quantities in ordinary illuminating gas. and has a characteristic disagreeable odor somewhat resembling that of garlic. Its "critical temperature" is 37° C. (about <)8°.6 F.) : that is to say, no matter how great the pressure to which it may be subjected above .37° it will remain gaseous, while at 37° a certain pressure, called the "critical pressure," is necessary and sullicient to liquefy it ; the critical pressure of acetylene is (iS at- mospheres. Acetylene burns with a brilliant llame and is u.sed as an illuminant. It is best made for scientific as well as for industrial pur- poses by the action of water on the carbide of calcium (q.v.). It is thus produced, for in- stance, in bicycle "gas lamps." The various apparatus devised for the manufacture of acety- lene produces it either in the gase(ms state or, by innnediate compression, in tlic liquefied state. Ve will distinguish two types of apparatus. In the first, the carbide is contained in an appropriate reservoir, into which water is introduced at a required rate. Such apparatus is rather inconvenient and somewhat dangerous, for the reason that in the mass of carbide con- siderable 'ise of temperature may occur at the point inuncdiately attacked by water; besides, a crust of lime may form on the surface of a lump of carliide, and when the water at last penetrates to the core of the lump a sudden and more or less violent reaction may ensue ; all of which would naturally result in uneven genera- tion of gas, variations of pressure, and, perhaps, the explosive inflannnation of the gas. In the second type of api)aratus, on the contr."ry, the carhidc is thrown into a considerable mass of icater, whereby tindue elevations of temperature and irregularity of action are completely avoid- ed. As the presence of impurities in acety- lene adds considerably to the danger of using the gas, various methods of purification have been proposed. Now, the nature and quantity of im- purity in acetylene depends entirely on the com- position of the carbide used in its manufacture, and a very pure acetylene has been produced on quite a large scale sim])ly by employing a pure carbide. With air or oxygen acetylene forms extremely explosive mixtures; mere external friction of a vessel in which such a mixture is contained may cause an explosion. But even when isolated and pure acetylene is explosive if kept under pressure of more than two atmos- pheres; and it is very dangerous indeed when preserved in liquid form. It has, instead, been stored in solution in ordinary acetone, which absorbs considerable quantities of it. If the pressure vinder which the gas is dissolved in jicetone is not very gieat, explosion can occur only in the gaseous volume ;ibove the surface of the liquid: the dissolved portion of the gas does not take part in the explosion. Under any circumstances, sudden com])ression of a volume of acetylene may cause an explosion. Acetylene is slightly, if at all, poisonous; it is certainly mueli less poisonous than ordinary illuminating gas.

Acetylene contains a high percentage of carbon, and the amount of lie at generated in its combustion is very large. These are the causes to which its high illuminating power is due; for. in order that a llame may be luminous, it must contain a large amount of carbon particles, ami its temperature nnist be high enough to keep those particles in a state of incandescence. Tn order that acetylene may yield a large amount of light, it must be properly burned. The numerous burners devi.scd for this purpose are constructed with a view to burning either pure acetylene or mixtures of