ACETIC ACID.— Manganese Acetate. Acetate of Soda. 51
coal and decomposed carbonaceous matters of thesalt are separated; and the solution, upon evapora-tion to dryness, yields a very pure and nearly colour-less product: 140 lbs. of this salt is the averageproduce of 1 ton of wood.
Manganese Acetate, Mn(C 2 II 3 0 2 ) 2 .—This com-pound is prepared by dissolving pure manganesecarbonate (MnCO. s ) in acetic acid, evaporating thesolution, and crystallizing. The crystals are of therhombic prism, and occasionally in plates of anamethystine colour; they are permanent in air,soluble in alcohol and in about three and a halftimes their weight of cold water.
On the large scale this salt is manufactured byprecipitating a solution of the manganous sulphateby one of lime acetate, and agitating the liquor todecompose the whole of the manganese salt.
MnS0 4 + Ca(C 2 II 3 0 2 ) 2 = Mn(C 2 H 3 0 2 ' 2 + CaS0 4 .
It sometimes happens that a portion of the man-ganese salt is not acted upon by the acetate of lime ;in this case a concentrated solution of acetate oflead is employed towards the end of the process toeffect the complete decomposition. The mixed pre-cipitate of sulphate of lime and lead is filtered off,and the filtrate evaporated and crystallized, or, ifdeemed necessary, used directly. The best acetateof manganese is made by adding to 4 parts of man-ganous sulphate, dissolved in 3 parts of water, 7parts of crystallized acetate of lead dissolved in 3parts of water, agitating the solution, and drawingoff the clear liquor for use.
Acetate of manganese is used in dyeing and calicoprinting, to give a brown colour to fabrics. Itsprinciple of action depends upon the further oxida-tion of the manganese. The cloth is well steepedin a concentrated solution of the acetate of man-ganese, and printed; it is then passed through abath containing bleaching powder, which oxidizesthe manganese, producing a brown colour on thatwhich, previous to its immersion in the bleaching orchloride of lime solution, was colourless.
Sodium Acetate, Acetate of Soda; terre folieeminerale, French ; NaC 2 II 3 0 2 .—This salt is formedby dissolving carbonate of sodaFig. 36. ; n acetic acid, evaporating the
a A solution, and setting the liquoraside to crystallize, The crystals. 7 are oblique rhombic prisms (Fig./ 30) soluble in 3 parts of cold,
in a less quantity of boilingwater, and in 5 of alcohol. Their composition isNaC 2 II s 0 2 + 3II 2 0.
This salt possesses a pungent but not disagreeabletaste. It is soluble in 3-9 parts of water at 44° Fahr,(6° C.), in 2‘4 at 99° Fahr. (37° C.), and in 1-7 at117° Fahr. (48° C.). According to Gerardin, 100parts of alcohol at 0-9904 dissolved 38 parts ofthe crystallized salt at G5° Fahr. (18° C.). Thesolubility diminishes if the alcohol is more concen-trated ; alcohol 0-832 dissolves only 2-1 parts. "Whenthis salt is exposed to dry air it loses its threeequivalents of water, but regains them in a moist
atmosphere. After -being melted this salt is deli-quescent, and takes up 7 equivalents of water; itthen becomes a liquid supersaturated solution, whichcrystallizes with evolution of heat immediately afragment of dry or crystallized or sodium acetate isthrown into it.
On the large scale the manufacture may be carriedout in the following way: — A filtered solutionof the common acotaxe of lime is precipitated byone of sulphate of soda at 98° or 100° Fahr. (36° to38° C.), till the whole of the lime is thrown downas sulphate. (This process is not economical, onaccount of the formation of the double sulphate ofcalcium and sodium, CaUa.,(S0 4 ) 4 .) The strengthof the solution of the lime-salt is 1-116, and of thesoda solution 1-250; or the sulphate of soda may beadded in powder, and the whole well agitated untilno further precipitation of sulphate of lime takesplace, using the precaution, however, of adding thesulphate of soda sparingly, so as to prevent itsexcess. The mixture, after thorough agitation, isdrawn off into a deep vessel and allowed to repose;and when the precipitated sulphate of. lime hascompletely settled, the clear liquor is siphoned offand conducted to the evaporating pans for crystal-lization, the remaining lime-salt being washed withsuccessive portions of water, till the whole of theacetate of soda is separated. The first washingsmay be added to the strong solutions in the eva-porating pans, and the others' retained for dissolvingfresh portions of acetate of lime for subsequentdecomposition. The process now most generallyadopted is to distil the aoetate of lime (after purifi-cation) with sulphuric acid, and saturating the aceticacid evolved with sodium carbonate.
Occasionally the solution of rough acetate of sodais filtered, and the precipitate washed in the follow-ing manner: — One or two backs are provided,according to the size of the factory; these areplaced over two cisterns, each cistern being con-nected with both the backs by pipes branching fromthe latter to both cisterns ; by means of a stop-cockin those connecting pipes the communication ineither back may be cut off at will when required, asseen in Fig. 37. The backs are either square orcircular, having false bottoms, in which are filters ofstout twilled flannel. The charge from the decom-posing pan is run on to one of the backs and filtered,till the whole of the strong liquor has passed intoone of the cisterns; the connection with this cisternis then cut off, and when the washing of the residuecommences the pipe communicating with the othercistern is opened, and conducts the washings into it.A fresh charge may then be introduced into thesecond back, and the pipe reaching to the cisternholding the strong liquor opened. Thus the strongliquor is always obtained by itself ready for evapora-tion. Another advantage is, that while the residuein one back is in the course of being washed, theother may be filtering off strong liquor. The washingis continued till the percolations are nearly taste-less; the residuum is dug out of the filters withwooden spades; iron spades cannot be used, as they