118 On a Mode q/' rendering Substances incombustible. 



there are peculiar dangers; but if a person were standing very 

 near the fire, the ammonia would in part be evaporated, and 

 the acid remaining would be enough to injure the fabric. 

 There are however cases, such as curtains, to which this could 

 not apply, and where it would be valuable. 



Sir William Burnet's liquid is chloride of zinc: he uses it 

 for preserving wood and canvas, and also for preventing fire. 

 I am certainly surprised that more use has not been made of 

 it, being, as far as I have seen it, so efficient. I believe the 

 manner in which the chloride of zinc acts is very similar to 

 that of the sulphuric acid, destroying the organic matter on 

 the approach of heat, and rendering it incombustible. It can 

 he introduced into wood at a specific gravity of 2000, I be- 

 lieve ; sulphate of ammonia cannot easily be used above 1200. 

 By heating the solution more may be attained. Sulphate of 

 ammonia is cheap and easily procured and used, not hurting 

 anything with which it may come in contact, and therefore 

 more easily managed in households. 



The chloride of zinc is said to unite with the fibre. This 

 cannot be said for the sulphate of ammonia. It would not, 

 however, come from the centre of a beam of wood, even if 

 immersed in water, as the water enters with great difficulty 

 into wood ; and the solution itself cannot be introduced with- 

 out forming a vacuum in the saturating vessel, and so remo- 

 ving all the air from the wood. 



The first time I used this solution I found a large quantity 

 of mould formed, and indeed it contains all the elements to 

 increase its growth. The second time the solution was boiled 

 in an iron vessel, and no mould formed on it ; on the contrary, 

 mould was destroyed by it. The sulphate of ammonia dis- 

 solves iron rapidly, and forms a double salt which is delete- 

 rious to such growths. I imagined any other metallic salt 

 would do, and used ordinary chloride of manganese prepared 

 in the laboratory, which killed all such fungi rapidly, and no 

 more have grown after standing eleven months in contact with 

 organic matter. 



I believe there are many ways in which this may be used. 

 My wish was to find a substance suited for building fire-proof 

 ships, and 1 believe this would do ; at any rate the ships would 

 be fire-proof, experience could alone tell if any other objection 

 followed. It does not render the wood hard, heavy or brittle. 



I believe it would be of the greatest advantage in mills, which 

 now suffer so much from fire, diminishing or rather entirely 

 removing the expense of insurance. It does not hurt colours ; 

 so that even coloured goods might be dipped when kept long 

 in one place, or when sent in vessels abroad. Possibly some 



