compounds called lime soaps, formed in hard waters.  Now in washing and scouring wool and other fibres, these sticky lime soaps adhere so pertinaciously that the fibres, be they of wool, silk, or any other article, remain in part untouched, impermeable to mordant or colouring matter, and hence irregular development of colour must be the consequence.  Also an unnatural lustre or peculiar bloom may in parts arise, ruining the appearance of the goods.  In some cases the lime soaps act like mordants, attracting colouring matter unequally, and producing patchy effects.  In the dye-baths in which catechu and tannin are used, there is a waste of these matters, for insoluble compounds are formed with the lime, and the catechu and tannin are, to a certain extent, precipitated and lost.  Some colours are best developed in an acid bath, such as Cochineal Scarlet, but the presence of the bicarbonate of lime tends to cause neutralisation of the acidity, and so the dyeing is either retarded or prevented.  Such mordants as “red liquor” and “iron liquor,” which are acetates of alumina and iron respectively, are also wasted, a portion of them being precipitated by the lime, thus weakening the mordant baths.

Ferruginous Impurities in Water.—­Iron in solution in water is very objectionable in dyeing operations.  When the iron is present as bicarbonate, it acts on soap solutions like the analogous lime and magnesia compounds, producing even worse results.  In wool scouring, cotton bleaching, and other processes requiring the use of alkaline carbonates, ferric oxide is precipitated on the fibre.  A yellowish tinge is communicated to bleached fabrics, and to dye bright and light colours is rendered almost out of the question.  You may always suspect iron to be present in water flowing from or obtained directly out of old coal pits, iron mines, or from places abounding in iron and aluminous shales.  Moreover, you sometimes, or rather generally, find that surface water draining off moorland districts, and passing over ochre beds, contains iron, and on its way deposits on the beds of the streamlets conveying it, and on the stones, red or brown oxide of iron.  All water of this kind ought to be avoided in dyeing and similar operations.  The iron in water from old coal pits and shale deposits is usually present as sulphate due to the oxidation of pyrites, a sulphuret or sulphide of iron.  Water from heaths and moorlands is often acid from certain vegetable acids termed “peaty acids.”  This acidity places the water in the condition of a direct solvent for iron, and that dissolved iron may cause great injury.  If such water cannot be dispensed with, the best way is to carefully neutralise it with carbonate of soda; the iron is then precipitated as carbonate of iron, and can be removed.