If wool is dyed in a dilute solution of Magenta (hydrochloride of rosaniline), the whole of the base (rosaniline) is taken up, and the whole of the acid (HCl) left in the bath, not, however, in the free state, but probably as NH_{4}Cl, the ammonia being derived from the wool itself. A further proof of the acid nature of lanuginic acid is that wool may be dyed a fine magenta colour in a colourless solution of rosaniline base; for since rosaniline base is colourless, and it only forms a colour when combined with acids, the fibre has evidently acted the part of an acid in the combination. #Chemical Properties. Action of Alkalies.#--Alkalies have a powerful action on wool, varying, of course, with the nature of the alkali, strength of solution and temperature at which the action takes place. An ammoniacal solution of copper hydroxide (Schweizer's reagent), has comparatively little action in the cold, but when hot it dissolves wool fairly readily. The caustic alkalies; sodium hydroxide, NaOH, or potassium hydroxide KOH, have a most deleterious action on wool. Even when very dilute and used in the cold they act destructively, and leave the fibre with a harsh feel and very tender, they cannot therefore be used for scouring or cleansing wool. Hot solutions, even if weak, have a solvent action on the wool fibre, producing a liquid of a soapy character from which the wool is precipitated out on adding acids. This action of alkalies has an important bearing on the scouring of wool, for if this operation be not carried out with due care there (p. 010) is in consequence great liability to impair the lustre and strength of this fibre. From microscopical examination this effect of alkalies is seen to be due to the fact that they tend to disintegrate the fibre, loosen and open the scales, this is shown by contrasting the two fibres A and B shown in figure 4, A being a normal wool fibre, B one strongly treated with an alkali. The alkaline carbonates have but little action on wool, none if used dilute and at temperatures below 120 deg. F. [Illustration: Fig. 4.--Showing the Effects of Scouring Agents on the Wool Fibre. A. Unscoured Fibre. B. Badly Scoured Fibre.] Soap has practically no action on wool, and is therefore an excellent scouring material for wool. The carbonate of ammonia is the best and has the least action of the alkaline carbonates, those of potash and soda if used too strong or too hot have a tendency to turn the wool yellow, the carbonate of potash leaves the wool softer and more lustrous than the carbonate of soda. The influence of scouring agents on wool will be discussed in the chapter on cleansing wool fabrics in more detail. Caustic or quick-lime has a similar injurious action on the wool fibre as the caustic alkalies.