408 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



but that they hold it with greater affinity, not allowing- the gas to escape 

 and affect the atmosphere, at the same time parting- with it more regularly 

 «.nd effectively to the goods. The alkalies used were soda and potash. 



In 1798 Mr. Tennant, of Glasgow, patented a process for using a solution 

 of lime for absorbing tlie chlorine. 



Shortly after, the hydrate of lime (slacked' lime) was substituted for 

 lime water. And this is the preparation now used for bleaching, under the 

 name of chloride of lime. 



The best bleaching powder of commerce seldom contains over 30 per 

 cent, of chlorine available in bleaching. 



To prepare chloride of lime for bleaching, an aqueous solution is requi- 

 site. For this purpose a quantity is put into a large vessel filled with 

 water, well stirred, and allowed to settle. This is called the stock liquor. 

 'There are no definite proportions. Every bleacher makes up his stock-vat 

 to a certain sti-ength indicated by his hydrometer. 



■Care is taken that this liquor is protected from the air as much as possi- 

 ble, as the lime absorbs carbonic acid, and the chlorine being set at liberty, 

 •occasions a loss. 



The goods to be bleached are cleansed from adhering dirt or grease, in. 

 some cases by boiling in alkaline solutions, in others by simply washing. 

 'They are then laid loosely as possible in the bleaching liquor. 



The vessels which 'Contain this liquor are large, made either of wood or 

 :stone, and are termed bleaching-vats, or troughs. To prepare this liquor, 

 these vats are filled with water, and a quantity of the stock liquor added 

 iintil the required strength is attained, which is indicated by its action on 

 .sulphate of indigo, in what is called the test glass. 



This is a cylindrical glass measure, with marks or gradations on its 

 side. It is filled, for example, to tlie lowest mark with the sulphate of indi- 

 go; the liquor is added drop by drop until the color of the indigo is de- 

 :stroyed. The quantity taken to effect this is denoted by the graduations 

 above; the weaker the liquor, the greater number of the graduations re- 

 quired. Each of these graduations is termed its degree. 



The goods are allowed to steep in this liquor for several hourg| vai^ying 

 .according to the nature of the goods. • 



. The bleaching properties of ozone have excited considerable attention 

 during a few years, and enough is known of it to induce the opinion 

 that when easy methods of producing and applying it arc discovered, 

 it will be of great value in the arts. 



Next to bleaching comes dyeing. Straw is colored blue by a boiling 

 bot solution of indigo in sulphuric acid, called saxon blue, diluted to the 

 desired shade^ yellow by decoction of tumeric; red by cochineal, salt of 

 tin, and tartar. Brazil wood is also used for dyeing straw. And what 

 may be said of dyeing fabrics generally will apply to straw. 



Straw has been used to some extent as a material for white paper for 

 many years; but the loss of material, from its brittle nature, during the 

 processes of manufacture, and other circumstances, more than counterbal- 

 lanced the advantage gained from the abundance of the supply, until quite 

 recently, when the very high price of linen and cotton rags, and improve- 



