288 The Art of Dyeing . 



stirred. Although chloride of lime may possess all these 

 properties it is not sufficient for the manufacturer. We 

 must test its bleaching power, for this is the property 

 which gives it its value. 



There are many chemical tests for this purpose, but they 

 are too troublesome to be employed with advantage by the 

 printer and bleacher. The following test effects the object 

 more quickly: a mordant is prepared of 4 loths (1*87 oz.) 

 alum, 2 loths (-938 oz.) sulphate of iron, 6 loths (2-81 ozs.) 

 sugar of lead, and 32 loths (15 ozs.) water. Some calico 

 is now moistened with the clear solution, washed in water 

 after hanging 48 hours in the air, and dyed with cochineal. 

 The calico acquires a reddish-brown colour, and affords an 

 excellent means of testing the bleaching power of the 

 chloride of lime. 



This reddish-brown colour from cochineal will be de- 

 stroyed by the chloride of lime, and so much the more 

 rapidly and completely in proportion to its strength. If we 

 bring, for example, a drop of the solution of good chloride 

 of lime, consisting of 1 part chloride of lime in 100 water, 

 in contact with the calico, a whitish-yellow spot is imme- 

 diately produced and the colour is dissipated. If the solu- 

 tion of chloride of lime is still more diluted, as for example, 

 1 chloride of lime with 200 water, a yellow spot is produced 

 upon the cotton by the contact of a drop, but is less pure 

 and regular. By a proportion of 1 chloride of lime and 

 300 water less effect is produced, and by greater dilution a 

 point is attained where no remarkable action ensues. This 

 lies in good chloride of lime with a proportion of 1 chloride 

 of lime to 1000 water, while, from this a drop, when placed 

 on cotton, produces a sensible bleaching effect. 



It will be readily observed, that by some practice, this 

 procedure affords a sure and easy method of estimating 

 the strength of chloride of lime. But it is desirable, in 

 order to go properly to work, to make a scale of the 

 cotton by means of chloride of lime, while solutions of the 

 chloride are made in 100, 200 and 300 parts of water, a 

 drop of each solution placed upon the cotton, and the latter 

 reserved for future trials. 



{To be continued.) 



