COMMONPLACE NOTES. 



629 



COMMONPLACE NOTES. 

 By the Secretary, Superintendent, and Editor. 



Use of Acetylene Eesidue. 



We are frequently asked whetEer the residue from the calcium 

 carbide used in the generation of acetylene gas has any value in the 

 garden. 



Calcium carbide is made by heating lime and charcoal together in 

 an electric furnace. The calcium and carbon combine and the compound 

 thus formed interacts with water when it is moistened, setting free 

 acetylene gas, and leaving behind slaked lime as a white residue. If the 

 substances used in the manufacture of the carbide were quite pure, 

 nothing but slaked lime and any excess of water used would remain; 

 but there are almost always some compounds of sulphur and lime, 

 and phosphorus and lime formed, which might have an injurious 

 action upon plants if they came in contact with them. These sub- 

 stances are, however, present in very small quantities^ and if the 

 residue be exposed to the air for two or three weeks the former 

 become oxidized and quite innocuous, while the latter are never present 

 in sucK quantities as would be likely to do harm. After exposure to 

 the air for a little time, therefore, the residue is exactly the same as 

 the material obtained by slaking ordinary burnt lime and allowing it to 

 be similarly exposed (with the addition of a very small proportion of 

 harmless impurities), and it may be used for any of the purposes for 

 which ordinary slaked lime is used. 



If, therefore, the residue is first exposed to the air for a time before 

 it comes in contact with the roots of plants, it may be spread on the 

 soil at the rate of about half a bushel to the square rod, as evenly as 

 possible, and then dug in, and all the beneficial effects of the applica- 

 tion of slaked lime to the soil may be expected to follow. It will 

 counteract sourness in the soil and mitigate the evils which arise from 

 that condition, and in clay soils will cause the minute particles of clay 

 to coagulate and make the soil more porous, easier to work, better 

 aerated, and warmer than it was before. 



It is also said to be of value in cesspools (see " Journal of the Board 

 of Agriculture," 1909). The refuse may be run into the cesspool, 

 and the lime will cause all solid matter to settle, leaving a clear liquid. 

 The sohd precipitate may be dug out at the end of the year, and will 

 form a valuable manure. 



Suggested New Stock for Pears. 

 Our attention has lately been called by one of our Fellows to a 

 new stock for Pears — viz. Pyrus ussuriensis { — P. sinensis.) We under- 

 stand that it has hardly (if at all) been tried in this country, although 



