BAIRD ^T^TLOCK (LONDON) LTD. 



451 



453 



454 



452 



451 s Animal Balance, to weigh up to 20 kilos, with stout copper pan 25 centimetres long by 



22 by 22 centimetres . . . . . . . . . . . . . each 2 7 



452 s Animal Balance, suitable for guinea-pigs, rats, mice, etc., to weigh 10 grammes to i kilo, 



with copper pan . . . . . . . . . . . . . . each 015 



453 s Apparatus of Copper, Brazed Joints, for Heating Cultures to separate spore-bearing 

 micro-organisms, by Professor C. Balfour Stewart. Price, on stand, but without ther- 

 mometer or condensation tube . . . . . . . . . . . . each 



(Extract from CentralUatt fur Bacteriologie, March, 1900.) 



" Those who have occasion to work with spore-bearing micro-organisms must often have felt the want of 

 an apparatus which would keep at a constant temperature of between 70 C. and 80 C. 



" An application of Meyer's hot air bath such as is used in chemical laboratories suggested itself as being 

 most applicable to the purpose ; several of these were made and are now kept in everyday use in this laboratory. 

 They maintain a constant temperature of 80 C. without any attention, and are always ready for placing tube 

 cultures in, and, what is more important, the cultures may be left without any fear of their becoming heated 

 above 80 C. 



" The apparatus is similar in construction to Meyer's hot air bath, except that it is larger than those 

 generally used and has no outlet from the bottom of the inner chamber. 



" The inner chamber is 18 cm. deep and g cm. in diameter, and will take seven or eight tubes ; it is advisable 

 to have a condensation tube of i metre in height. (1.5 metre is most suitable.) 



" In use. A small quantity of pure benzole B.P. 80 C. is poured into the outer jacket through the hole 

 for the condensation tube and the tube is reinserted. A small flame below will keep the benzole boiling, and as 

 the vapour condenses in the condensation tube and runs back, very little is lost. 



" Thp inner chamber is filled to about one-third of its depth with water at 80 C., the water retains its heat 

 when the lid is removed, and acts as a good conductor of heat to the culture tubes when they are placed in it. 

 If water is not put in the inner chamber the heated air escapes when the lid is removed and it takes a long time 

 for the culture tubes to become heated, whereas, if water is in the inner chamber and the culture tubes put in 

 when the thermometer registers 80 C., it is found that there is only a fall of 10 to 15 C. and the thermometer 

 rises to 70 C. in a few minutes. 



" The tubes are left in for 15 to 20 minutes after the thermometer has risen again to 70 C., so during that 

 time they will have been kept at between 70 C. and 80 C., and for most of the time over 75 C." 



1 16 



454 Gas Burner for Incubators, with small luminous pointed flame and mica cylinder. 



A. Without stopcock . . 



B. With stopcock . . .... 



each 





 



CROSS STREET HATTCTNT GARDEN, E-C 



98 



