1885.] 



Studies of Disinfectants by New Methods. 



261 



The — sign in the table denotes " no growth," the ■+- sign means 

 that on the day denoted in the upper column the gelatin began to 

 liquefy, and growth to appear. 



Phenol and Gresol. — These experiments were made by the " drop " 

 method. 



Weighed quantities of pure crystalline phenol and of pure liquid 

 cresol* w r ere dissolved in 20 per cent, alcohol in such proportion that 

 the strength was exactly 1 per cent. Water which had been infected 

 with the bacterium was measured from a burette into test-tubes, and 

 definite quantities of the phenol or cresol solutions added ; the volume 

 of the whole being kept at 10 c.c, e.g., 3 c.c. of phenol solution, and 

 7 c.c. of the infected water would equal 0'3 per cent., 1 c.c. of phenol 

 solution and 9 of the infected water would equal 0*1 per cent., and so 

 on. At the end of twenty-four hours nutrient gelatin was infected 

 by means of dipping a clean recently ignited platinum wire in the 

 liquid, and then inserting the wire for a second or two in the gelatin, 

 which had been previously liquefied. The following short table sum- 

 marises these experiments ; as before, the — sign denotes no growth, 

 the + sign denotes the first appearance of evident growth and lique- 

 faction. 



Phenol and Cresol. 



Days 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 



10. 



At 15-5° a— 





















Phenol 0*01 per cent 











+ 











jj 



005 „ 











+ 













o-io „ 











+ 











?> 



0-25 „ 











+ 













0-50 „ 





















Cresol 



o-oi „ 











+ 













0-05 „ 





















)> 



oio „ 











+ 











55 

 55 



0-25 „ 



0-50 „ 























Control 



+ 



















At 35-5° 



a— 





















Phenol O'Ol per cent 









+ 













55 



0-05 „ 











+ 











55 



010 „ 













+ 









55 



025 „ 





















Cresol 



001 „ 









+ 













55 



0-05 „ 











+ 













o-io „ 















+ 







55 



025 „ 





















* The cresol used was the purest commercial sample, and was obtained from 

 Messrs. Calvert. 



