278 The Art of Dyeing. 



Since the violet blue is a very agreeable colour, so the 

 above observations suggest a method of imparting it to 

 chemical blue. Mix, therefore 1 lb. of solution of ammonia 

 with 300 lbs. water, pass the goods through it, and allow 

 them to dry without washing tbem. 



Much ammonia destroys chemical blue like potash and 

 soda. 



As ammonia is an alkali, it prevents the action of acids. 

 It removes, therefore, spots which have been produced 

 upon coloured cotton by vinegar, lime juice, sulphuric 

 acid, &c, and is, therefore, useful in practice as it produces 

 no spot itself; but, in consequence of its volatility, soon 

 disappears. It is to be observed, therefore, as was noticed 

 with vinegar, that we can only expect a result from the 

 use of ammonia when the spot is not too old and cannot 

 be washed out. 



Lime. — Quicklime evolves heat in contact with water, 

 and becomes slaked lime. In this state it dissolves in 

 water. Lime-water contains but very little lime. The 

 quantity dissolved diminishes with the heat of the water. 

 Thus, 656 lbs. of water at 32° dissolve 1 lb. lime, and 753 lbs. 

 water at 59° dissolve only a lb. of lime, while of boiling 

 water 1280 lbs. are required for the same quantity of lime. 



As heat is disengaged in slaking lime, we must, in order 

 to obtain strong lime-water, add the remaining water after 

 cooling, or place the whole mixture in a cool place and stir 

 it frequently. 



Calico can without great risk be boiled with lime-water 

 or milk of lime, when it is carefully washed, and then passed 

 through an acid to remove any lime still adhering to the 

 fibres. Otherwise the lime makes the fibre rough, brittle 

 and tender. 



Lime especially injures calico under the influence of light. 

 If a portion of calico is saturated with lime-water, laid for 

 some days in the sun, and again saturated and laid out 

 three or four times, the stuff becomes remarkably white, but 

 so tender that it can be pulled to pieces with the fingers. 

 Lime acts upon most colouring matters like mordants. 



Calico which contains lime is therefore dyed as if it 

 were mordanted. Such calico cannot be employed to form 

 a white base out of the same ground, unless the lime is 



