10 SODA ASH. 



and unpleasant insects, ants, bugs, &c. Eoofs of pasteboard or of wood 

 which have been painted with the mixture keep dry, and withstand the 

 effects of rain and snow. 



"Wood impregnated with sulphate of copper will not last longer in 

 sea-water than other wood. It is quite as much attacked by the sea 

 worm as when in its natural state. On the other hand it has been 

 proved that wood impregnated with sulphate of copper will have longer 

 durability in the soil than when either tarred or charred. 



The following statement of M. Brouzet to the French Academy may 

 also be of interest. He has a seat in the Cavennes Mountain, where he 

 cultivates silk-worms. The shelves upon which they breed are of pine. 

 During the period from 1853 to 1858 all his crops perished through 

 illness. In 1860 he was induced to make new shelves of pine impreg- 

 nated with sulphate of copper, and ever since the silk-worms have, been 

 in the finest and healthiest condition* 



At Saint Sebastian, in Spain, the piles of a wooden bridge standing 

 in the sea have been guarded against the attacks of sea-worms in the 

 following manner. Each pile is surrounded by a wooden box, and the 

 space between filled up with cement. After six years it was proved that 

 the piles were in perfect condition, whilst the outer boxes were com- 

 pletely riddled by the worms. 



SODA ASH.f 



BY MURRAY THOMSON, M.D., F.R.S.E. 



Soda Ash, or, as it is sometimes called in commerce, " Alkali," is a 

 preparation of soda largely used by the paper maker, and his use of it 

 has greatly increased since the scarcity of rags has compelled the intro- 

 duction of new sources of fibre. The process by which an almost un- 

 limited supply of soda ash can be produced we owe to the ingemuty of a 

 Frenchman, M. Leblanc, wdio published his process about the end of last 

 century. It was first practically applied at St. Denis in 1804. It was 

 proved then to be an eminently successful process, and though it early 

 commanded the esteem of our English manufacturers, yet it was not till 

 the repeal of the salt duty that it was adopted in this country, and one 

 of the first manufacturers to employ it was Muspratt of Liverpool. 



Previous to the introduction of Leblanc's process, our only source 

 of alkali was from the ash of seaweed, knowm under the name of 

 Barilla, w r hen it came from Spain, and Kelp, when it was made in the 



* See ' Coniptes Rendus de 1' Academie Frangaise,' vol. 54. 

 t From ' The Paper Trade Review.' 



