APPENDICES. 



149 



The carbonic acid gas is produced by acting with sulphuric acid upon 

 bicarbonate of soda or saleratus. The latter is first made into a thin 

 paste with water, using about 1 fluid ounce of water to each 2 ounces 

 by weight of the bicarbonate. Several seconds elapse after the 

 sulphuric acid comes in contact with the soda paste before the evolution 

 of the gas begins ; a foamy mass soon appears, consisting of variously- 

 sized bubbles, which rise up in the generator and finally burst, giving 

 forth the colourless and odourless gas. A fluid ounce of the acid will 

 evolve all of the gas from about 3 ounces of the bicarbonate, weighed 

 before it is mixed with the water. 



The bicarbonate has a tendency to settle at the bottom of the solution, 

 forming a compact mass upon which the acid acts very slowly. On 

 this account it is desirable to add the soda paste to the acid instead of 

 following the usual method of adding the acid to the soda. I have used 

 marble dust in place of the bicarbonate of soda, and the result obtained 

 by its use was as satisfactory as when the bicarbonate had been used ; 

 it possesses none of the adhesiveness of the bicarbonate, and con- 

 sequently does not form a compact mass in the bottom of the solution. 



The best results have been obtained when both the hydrocyanic acid 

 gas and the carbonic acid gas were produced in the same apartment of 

 the generator. 



The cyaniole is first dissolved in water, as described above, using 5 

 pounds of the cyaniole to each gallon of water, and for every 10 fluid 

 ounces of this solution use 9 ounces by weight of the bicarbonate. 

 The bicarbonate is first made into a thin paste with water, as above 

 described, after which it is added to the proper quantity of the cyaniole 

 solution and thoroughly stirred ; the whole is then added very slowly 

 to the proper quantity of sulphuric acid, previously poured into the 

 lower apartments of the generator. 



The following table will give a good idea of the proper quantity of 

 each ingredient to be used for the differently-sized trees : 



The hydrocyanic acid gas will be just as effective if twice the amount 

 of the bicarbonate of soda that I have recommended be used, together 

 with a sufficient quantity of sulphuric acid to evolve all of the carbonic 

 acid gas from it. This latter gas does not act as a diluent, as some 

 persons have supposed, but simply as a drier, its sole office being to 

 extract the moisture from the hydrocyanic acid gas, thus rendering the 

 latter gas harmless to the foliage of the trees confined in it. 



