and Laboratory Methods. 2211 



An Acid-Proof Table Top. 



Three or four years ago the writer saw in a pharmaceutical journal (Merck's 

 Report) a formula for a black finish for table tops. The article did not give the 

 author's name nor the original source of the formula, but stated that the method 

 was " used abroad." Further acknowledgment cannot, therefore, be made. The 

 formula was as follows : 



1. 

 Copper sulphate ..---. 1 part 

 Potassium chlorate ----- 1 part 



Water - - 8 parts 



Boil until salts are dissolved. 



2, 



Aniline hydrochlorate . - - - - 3 parts 



Water -------- 20 parts 



Or if more readily procurable : 



Aniline -------- 6 parts 



Hydrochloric acid ----- 9 parts 



Water -------- 50 parts 



By the use of a brush two coats of solution No. 1 are applied while hot. 

 The second coat as soon as the first is dry. Then two coats of solution No. 2 

 and the wood allowed to dry thoroughly. Later a coat of raw linseed oil is to 

 be applied, using a cloth instead of a brush in order to get a thinner coat of 

 the oil. 



The writer used this method upon some old laboratory tables which had been 

 finished in the usual way, the wood having been filled, oiled, and varnished. 

 After scraping off the varnish down to the wood, the solutions were applied, and 

 the result was very satisfactory. 



After some experimentation the formula was modified without materially 

 affecting the cost and apparently increasing the resistance of the wood to the 

 action of strong acids and alkalies. The modified formula follows : 



1. 



Iron sulphate ------- 4 parts 



Copper sulphate ------ 4 parts 



Potassium permanganate ----- 8 parts 



Water, q. s. - - - • - - - 100 parts 



2. 



Aniline - - 12 parts 



Hydrochloric acid ----- 18 parts 



Water, q. s. 100 parts 



or 



Aniline hydrochlorate ----- 15 parts 



Water, q. s. - - - - - - 100 parts 



Solution 2 has not been changed except to arrange the parts per hundred. 

 The method of application is the same except that after solution No. 1 has dried 

 the excess of the solution which has dried upon the surface of the wood is 



