BORIC ACID. 97 



then stick the two pieces together by a glue without smell. Thus, 

 after removing the point of one of these roots a conical hole is made 

 in it, arsenic placed in the opening s ) made, and closed by the piece 

 removed, which forms a natural plug. Place the celery so prepared 

 in the nests. Complete success will be obtained if precaution be taken 

 to accustom the rodents to this preparation by giving them first non- 

 poisoned celery. 



1 6. Arsenic Acid, As.Pg. — Preparation. — By oxidizing arsenious 

 acid by nitric acid. 



Properties. — Arsenic anhydride is a white solid. It dissolves 

 slowly in water. It is a more violent and more rapid poison than 

 arsenious acid. 



Use. — 'Arsenic acid has been proposed for the disinfection of seed- 

 corn. A powder is prepared with 9 parts of lime and 1 of arsenic 

 acid, with which the corn kept moist is sprinkled in the proportion of 

 31 lb. per 2f bushels of grain. After twenty-four hours the seeds 

 were dried and sown. 



17. Boric Acid, B._,03. — Occurrence. — Occurs in nature some- 

 times free, sometimes combined with bases. 



Preparation.— By decomposing borax (sodium diborate) by hydro- 

 chloric acid. Borax is dissolved in four times its weight of water and 

 hydrochloric acid added to a decidedly acid reaction. Boric acid 

 crystallises out as shining scales on cooling, is drained and washed 

 with cold water. 



Properties. — Boric acid occurs as shining scales, but Uttle soluble 

 in water ; 4 per cent at 20° C. It is a weak antiseptic. To preserve 

 meat for three weeks it must be steeped in a 4 per cent solution. 



Use. — Kuhn has examined its antiseptic power on bacteria. A 



1 per cent solution does not stop their growth. A 2 per cent solution 

 stops the growth of bacteria. Even a 4 per cent solution does not kill 

 them. The alcoholic fermentation of saccharine solutions containing 



2 per cent boric acid is not completely arrested (Schwartz). Constantin 

 and Dufour tried without success a 2 per cent boric acid solution to 

 kill the mole disease of the mushroom {Mycogone perniciosa). 



