778 SOAP.— Marine (Cocoa-nut Oil).

lye, which produces the mottling by filtering slowlythrough the mass of soap. At Marseilles and otherplaces where olive oil is used in making soap, aquantity of sulphate of iron is added; in which casethe mottling is produced both by the black sulphideof iron and by the oxide of iron—the red portion—which latter combines with fatty acids, producing atrue ferruginous soap. The quantity of copperasrequisite is about 18 ozs. to 450 lbs. of oil or fat.It is added first mixed with weak lye, and should bepoured in during the cootion of the soap, and beforeit has acquired too much consistence. When thesoap is ladled out of the boiler, it is of a uniformslate tint; but as it becomes cool, the portion con-taining the iron solution separates into nodules, andby the trickling of the excess of lye through the massit becomes mottled. By varying the proportion ofsulphate of iron a tint is produced of a lighter ordarker hue. Soaps containing this have a rustycolour, owing to the oxidation of the iron, and thisshade may be deepened by the addition of Venetianred or colcothar, into the particular tint to whichthe French apply technically a term signifying hiddenred, and which upon the deep blue produces theappearance of marble, as seen in the variety knownas castile soap. This peculiar tint may be communi-cated as well before as after the true marbling; forwhich purpose it is necessary to thin out the col-cothar with water, and in adding it to incorporate itwell with the soap. Generally, in the preparationof mottled soap, less care is exerted in the choice ofmaterials than for white soaps, and the heterogene-ous mixture of fatty substances known as kitchenstuff usually forms one of the materials.

A well manufactured mottled soap cannot con-tain more than 33 to 36 per cent, of water, whereasgenuine curd soap contains 45 per cent., and yellowat least 52 per cent. The mottling being due to thepresence of sulphide of iron held in a state of sus-pension and demi-solution, it is evident that additionof water would cause the colouring matter to sub-side, and a white soap would result. The additionof water, technically “fitting,” is in fact the processused to obtain colourless soap, whether it be curd oryellow.

Cocoa-nut Oil Soap—Marine Soap. —Cocoa-nutoil is very easy to saponify, and is used to a con-siderable extent in the manufacture of white soap,as well per se as in admixture with other oils andfatty matters. The disagreeable odour is removedmost effectually and conveniently by boiling in awooden vessel by means of steam with a mixture of6 lbs. of sulphuric and 12 of hydrochloric acid toeach tun of oil. The oil so purified is heated in theboiling caldron, with the addition of a portion ofolive or some other readily saponifiable oil or fat,and the soda lyes are gradually introduced in theusual manner. Towards the conclusion of the pro-cess of saponification, a quantity of caustic potashlye is thrown in, and the boiling is continued as longas may be necessary. The soap thus formed requires,for its separation from the lyes, a much larger pro-portion of salt or other saline matter than the soaps

formed of tallow, palm oil, or olive oil; hence theusual mode of proceeding is not followed in theproduction of this soap. The principal distinctionbetween cocoa-nut oil and other oils and fats is,that while the latter are most readily saponified byweak lyes, cocoa-nut oil is quite unacted upon untilthe lyes have obtained a considerably higher degreeof concentration ; saponification then suddenly com-mences, and proceeds with extraordinary rapidity.Only the strongest soda lyes are employed in theproduction of cocoa-nut oil soap, and by taking pureand perfectly caustic lye, the use of salt in purifyingthe soap is dispensed with. Pure cocoa-nut oilhardens much too quickly to exhibit any distinctformation of curd, and is consequently incapable ofmarbling of itself; it is very white, translucent,exceedingly light, and forms a good lather, but hasalways a more or less offensive smell.

An important property of cocoa-nut oil is its powerof combining with more water than can ever beincorporated with tallow soap, and this propertyfrequently leads to dishonest practices. Cocoa-nutoil actually produces no greater quantity of soap thanan equal weight of tallow; but the soap from theformer can easily be made to absorb one-third morewater or lye, and at the same time exhibit no wantof consistence or softness, as would be the case withother soaps.

Cocoa-nut oil is not usually saponified alone, butis added to other oils for the purpose of producingquickly solidifying soaps containing a large propor-tion of water. When equal parts of cocoa-nut oiland tallow are used, the soap has the smell of com-mon tallow soap. The boiling is continued until aspecimen exhibits the proper consistence under thethumb. Tallow itself could not be saponified underthe same conditions; but the saponification beginswith the cocoa-nut oil, and the tallow is then saponi-fied by means of the presence of cocoa-nut oil soap.

The different varieties of this soap are marbled arti-ficially. The blue or red colouring matter is rubbedup with a little of the soap, or better, with a separateportion of good cocoa-nut oil soap, until the wholeacquires a red or blue colour. This is then placedin alternate layers with the colourless soap; and bystirring the mass together streaks and veins are pro-duced in all directions.

A mottled soap is also manufactured from cocoa-nut oil and palm oil, wherein the mottling is soperfectly effected by means of ultramarine and blackor brown oxide of manganese, that it is impossibleto distinguish it from the true mottled soap: 80cwts. of palm oil are made into soap in the usualway, and the spent lye pumped away, so that thecurd is left perfectly free; then 32 cwts. of cocoa-nut oil, 60 cwts. of lye at 20° B. added, and byslow degrees 14 cwts. of lye at 14° B. The wholeis then boiled till complete saponification takesplace. The colouring matter, 6 to 7 lbs. of ultra-marine (or whatever pigment may be used), is wellstirred into weak lye, and poured into the soapthrough the rose of a watering pot; the whole isthen boiled for half an hour to an hour, and the