ORCHIL.

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hydrometer for liquids lighter than water. The charge can be ready in threedays, but the quality is improved if worked for a week. Steam is admittedinto the casing by a pipe at the end opposite to the man-hole, and the tem-perature is kept up at such a height that the paste feels slightly uncomfortableto the hand—about 6o° C. or 140° F. The agitator is kept gently revolvingall the time. The admission of air is regulated according to the judgment ofthe manufacturer. The yield, for the quantity given above, is 540 lbs., orthree times the weight of the weed employed. An excess of ammonia rendersthe colour less stable, impairing its affinity for the fibre. It should be men-tioned that the blue shade makes its appearance first, and by proper manage-ment the change can, if desired, be arrested at this point. The red shadeappears when the joint action of air and ammonia is allowed to proceed to agreater length.

To prepare orchil liquor the weeds are boiled out with water, and strained;the extract concentrated to 8° to io° Tw., and then heated and agitated withammonia at 24“ of the ammonia-glass. Continual agitation is here not neces-sary. The arrangements for extracting the weed are various. It is generallyboiled in three successive waters, the first and second liquors being mixed andconcentrated, whilst the third serves for the first extraction of a fresh quantityof the weed. The weeds for paste and liquor should not be ground too fine,being bruised under edge-stones rather than pulverised. Certain additions arefrequently employed by manufacturers. Small quantities of red prussiate(ferricyanide of potassium) give the orchil a redder tone, whilst a slightaddition of a fixed alkali—generally carbonate of potash—serves to give anextra blue shade. An improved bloom and brilliance is imparted by a littletartar, or white argol.

The manufacture of cudbear is very simple. Orchil paste, made as abovedescribed, is dried at a steam-heat, and afterwards ground to a fine powder ina lac-mill. It is very generally weighted with common salt, and its appearanceis often factitiously improved by the addition of a little magenta.

Orchil paste varies greatly in quality, from variations in the lichens used inthe manufacture, from the degree of care and skill used in the process, andfrom the presence or absence of impurities. It may be too watery, containingnot more than 20 per cent of solid matter, in which case an extra quantity isneeded to produce the shades required. The amount of moisture is readilyfound by weighing out a quantity, and drying, at the heat of boiling water,till no further loss is experienced, and then weighing the residue. Orchil mayhave been overdone with ammonia, in which case its affinity for the fibre willbe feeble. If a cask of orchil paste, when first opened, gives off a pungentammoniacal smell, it may be pronounced faulty, but time and exposure to airwill correct this defect. Practical men often judge the quality of an orchilpaste by rubbing a little on the back of the hand, and permitting it to dry. Ifthe colour is well made a stain will remain on the skin, which cannot readilybe removed by washing in cold water or rubbing with a cloth. If the colouris bad, and especially if it be too ammoniacal, it is easily washed off withcold water.

Orchil is sometimes fraudulently mixed with extracts of logwood, sapan, &c.To detect these, about 50 grs. of the suspected sample are stirred up in3 ozs. of water; 50 drops of a solution of protochloride of tin, made by