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addition is continued at intervals during theBoiling till the greater part of it is ufed, but fomemud be referved to finilh the operation. Theliquor becomes more and more tenacious, andthe tough faponaceous part begins to feparatefrom the clear watery liquid below. This is afign that the procefs is going on well, and theboiling is continued till the whole contents ofthe copper are vifibly feparated into two parts,the tenacious white foapy mafs above, and theclear liquor below. When this is compleat,fometimes it is the cuftom to ftir in with poles afew pounds of common fait, which dill furtherpromotes this reparation, and gives the foapymafs a pally or granular confidence: but thisaddition (which is ed'ential in the potalh foaps)is not neeedary in thole with foda, and may beomitted. The fire- is then drawn, and thecontents of the boiler allowed to remain at redfor fome hours that the foap may colled morecompleatly, after which a cock is opened atthe bottom of the boiler, and the clear liquordrawn off. This latter is coloured and is nowno longer caudic, but as it dill contains fomealkali, it is mixed with the weaker leys andfrelh lime, and referved for future boilings.To the diff foapy pade left in the boiler a littlewater or v/eak ley is then added, and the firelit again, and when it has become fluid thereferved part of the firft ley is added, and thewhole brought to boiling. The foap being nownearly perfect, fmall portions of it are taken outwith a trowel and let to cool on a bit of date,and by the degree of diffnefs which it takeswhen cold the experienced workman judgeswhen-it is boiled enough. If it dill dicks tothe fingers and does not appear diff enough,more ley muft be added, and the boiling con-tinued till it is brought to the proper date.The fire is then again taken out and the clearliquor drawn off as before after remaining atred for a few hours. The fire is then againraifed, and the foap is again melted with alittle water to wafh out the adhering alkali,after which it is allowed to cool till it is fitto be taken out and framed. The frames arewooden troughs with a moveable bottom, intowhich the foap is poured while dill fluid, andallowed to remain for three or four days till iten °ugh- to be handled without finking in.The foap is then taken out and cut into longoblong flices with a brafe wire, and kept forfome time in an airy room till it has become ofthe requifite hardnefs, and is then fit for fale.According to the valuable memoirs on this

fubjeCt by Pelletier, Darcet, and Lenevrey-above quoted, 3 lbs. of oil will make 5 lbs. of-foap of the proper degree of drynefs for ufe,.but it continues to lofe weight by keeping, fothat when quite dry the above quantity isreduced to little more than 4. lbs. On theother hand when kept damp or ufed too foon,more than twice this weight may be made ofthe fame materials.

Such is the ufual way of making this kind offoap, which Gonfids of a gradual incorporationof the oil with the alkali by the afliilance ofheat, beginning with a weaker ley and con-cluding with the dronger. It is faid however thatfome of the Marfeilles manufacturers ufe thewhole alkali at once, and fucceed very well in thisway ; nor is it eafy to fay why this graduateddrength of alkali and thefe repeated interruptionsof the procefs during the coolings and fettlingsare required, and why it might not all be madeeconomically by one continued boiling. Never-thelefs, the interrupted method feems to be thatwhich is by much the mod commonly ufed, andprobably experience would prove its utility in-the large way.

It is not eflential to employ heat in producinga good foap, for the union between the oil andalkali will be perfedl by a fufficient length oftime of digedion if the ley be drong enoughsThus a very pure foap is fometimes made formedicinal purpofes in the following way : d mix'in a marble mortar or any veffei not metallic,any quantity of olive oil with half its weight ofa drong ley of caudic foda. The oil fliould beprevioufly melted in cafe it has become clottedby age. Stir them well together and they willimmediately unite into a thick white mafs, andcontinue the dirring for fome minutes feverattimes a day for about a week,, or till the foap isft-iff enough to - be put into wooden frames inthe ufual- way. Let it remain in the frames forthree or four days till it has confiderably hard-ened, and then cut it in flices and expofe it to afree current of air in a dry room till it iscompleat. This foap has at fird a very dronglixivial fmell, and a violently acrid tade, bothof which go off by expofure to the air, but ittakes nearly a month before the tade is mildor merely faponaceous.

Before we defcribe the manufacture of theother kinds of foap we may give in a few wordsthe refults of a feries of valuable, and apparent-ly accurate, comparative experiments on thefoaps made with foda and a variety of oilyfubftances, which were undertaken by Pelletier

ro;.