120

DYEING AND CALICO PRINTING.

LIME SALTS.

Hypochlorite of Lime.

Hypochlorite of lime, Ca0,C10, generally known as chloride of lime, occursin commerce chiefly in the solid state. Fluid chloride of lime is simply amilk of lime saturated with chlorine, and appears as a yellow fluid possessinga peculiar odour. As access of air causes decomposition of the fluid chloride,it must be kept in closed vessels. In the solid state chloride of lime is awhite mass, very hygroscopic, and easily decomposed by the adtion of thecarbonic acid of the atmosphere. Hypochlorite of lime is most extensivelyemployed as a bleaching agent, in very dilute solutions for the scouring ofwoven fabrics, in fixing and shading colours, and in printing to remove coloursin order to show a white ground. Of the methods of preparing and estimatingchloride of lime we shall speak more fully under the head of Chlorimetry.

A solution of hypochlorite of lime has but little effedt upon colouring-matters. This influence is increased by the addition of such acids or salts ascause the decomposition of the hypochlorite and the formation of free chlorineor hydrochloric acid. The powerful affinity of chlorine for hydrogen is inmost cases the cause of the bleaching power of the hypochlorite of lime, andthis affinity may produce its effedt in two ways:—

x. By the diredt removal of the hydrogen from the organic matter.

2. By decomposing the water in which the hydrogen and chlorine arein combination, and setting free the oxygen to adt upon the carbon of thecolouring-matter, oxidising it to carbonic acid, and to again combine withthe hydrogen to form water.

We know, however, but little of the true adtion of chloride of lime.

AM MON I AC AL SALTS.

Ammonia.

Ammonia is not largely employed in dyeing and printing. It is used inscouring, to fix metallic mordants, to produce with cochineal a crimson colour,to fix murexide, to modify the shades produced by a variety of colouring-matters, but chiefly, as is the case with its salts, for ageing purposes,especially with heavy mordants. When pure it does not leave any residueupon evaporation, and should yield no precipitate with sulphuretted hydrogen.The following table shows the percentage of ammonia according to the

density at 62° F.Sp. gr. of the

Per cent of Ammonia

Sp. gr. of the

Per cent of Ammonia

Liquid Ammonia.

by Weight.

Liquid Ammonia.

by Weight.

0-875

34-694

0-930

18-280

o'88o

33 -II 7

°'935

16-883

0-885

3f558

0-940

15-502

o-goo

26-984

o-945

i4" I 35

o-gog

2 5'493

0-950

12-782

o'gio

24-019

o-955

11-444

°’9 I 5

22-561

0-960

10-119

o'g2o

21-118

0-965

8-808

O'925

19-961

0*970

7-511