

BAIRD &TATLOCK (LONDON) LTD. 



4681 

 4681 Lunge and Zeckendorf's Air Tester, complete in box, without solution 







DIRECTIONS FOR USE. 



The carbonic acid present in the sample of air is calculated from the number of times it is found necessary 

 to press the ball before the red colour is discharged. From the table given below it will be seen that the greater 

 the number of pressures required the less carbonic acid is there present in the air. Thus, if only a few pressures 

 are required, the air is very bad ; from 9 to 10 pressures, moderately good ; from 20 to 25, very good. In the 

 open air 40 to 50 pressures would be required. Also, the greater the amount of carbonic acid present, the sharper 

 the discharge of colour. In pure air the change is uncertain and a complete discharge difficult to obtain, but 

 in this instance 3 pressures would only cause a difference in the third decimal place. 



PREPARATION OF THE TEST SOLUTION. 



Dissolve exactly 5.300 grammes chemically pure sodium carbonate in about a J-litre of distilled water, then 

 dissolve in it o. i gramme of phenol-phthalin, heating slightly, cool to 18 C., and make up to one litre. This deci- 

 normal soda solution will keep in a closed bottle for a considerable time. For use introduce into 100 cubic centi- 

 metre flask 2 cubic centimetres of this solution, fill up with recently boiled and cooled distilled water to the mark 

 on shoulder, and use 10 cubic centimetres of this for each test. This -^ normal solution must be preserved in 

 a well-stoppered bottle, which, after each opening, is quickly re-stoppered. 



If the experiments are interrupted for any length of time, it is best to prepare the weak solution afresh. 



N. B. This weak solution will not keep more than one day. 



TABLE. 



10 6 



ICHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



