298 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Oil paints are rendered uninflammable by the addition of phos- 

 phate of ammonia and borax in the form of impalpable powders ; 

 mortar of plaster and asbestos, and asbestos paint, are still em- 

 ployed for preserving temporarily from limited exposure to a fire. 



In England, America and Paris, attempts have been made to 

 introduce under strong pressure, preserving solutions into fibrous 

 substances. Large establishments have been erected in different 

 countries for this purpose. Unfortunately the process by pressure 

 is still attended with the serious evil of introducing fireproofing 

 products into the outer part of the wood only; the solution pene- 

 trating to quite a limited depth. The process consists in removing 

 from the wood, by the aid of steam under pressure, a part of liquid 

 products which it contains. This induces a sort of distillation 

 of the inflammable products, for which solutions are substituted, 

 generally composed of ammonium sulphate or phosphate, boracic 

 acid or alkaline borate. 



The best result has been obtained by electi'icity. In the 

 Nodon and Bretonneau process fireproofing products have been 

 introduced through the whole mass of the wood, and this in a way 

 much more regular than by injection even under strong pressure. 

 A truly exceptional power of resistance to the attacks of fire has 

 been thus imparted. The quantity of fireproofing products depends 

 on the strength of the bath and the duration of treatment. It has 

 been ascertained by experiment that wood is really uninflammable; 

 that is to say, that it resists for quite a long time a very high 

 temperature, if it contains, according to its nature, from 15 to 20 

 per cent, of the salts employed. 



Fireproofing of Wood by Electricity. 



The successive operations and the apparatus for incorporating the 

 fireproofing salts into the mass of the wood are nearly the same as 

 those for the ageing of wood properly so-called. It is absolutely 

 necessai-y for the treatment that the wood should be both green 

 and not too hard. 



The total duration of the operation is 48 hours, divided into two 

 equal parts. At the end of the first period, the wood is reversed 

 (turned upside down). The wood thus treated has absorbed from 

 15 to 20 per cent, of its weight of the salts of the bath. These 

 salts penetrate to the heart of the cells and form a sheath around 

 the fibre. If the wood after drying is submitted to the action of 

 fire, the ammoniacal salts, which encompass the fibres, melt. On 



