200 



DR. R. ANGUS SMITH 



part is pressed between the palm of the hand and the 

 finger ; the other is pressed between the surface of the 

 nails and the first joint of the thumb. 



This apparatus requires a little experience to produce 

 confidence. Assistants have tried it along with Petten- 

 kofer's method and obtained remarkably accurate analyses, 

 with fewer errors. I have not yet used it in scientific in- 

 vestigationSj and scarcely even practically, although with 

 observing persons it is worthy, I believe, of all confidence, 

 and especially if used daily, as in certain proposed inspec- 

 tions would be the case. 



For practical purposes the state of the barometer may 

 be neglected. 



'^rd. The bulk of Air fixed, the Lime-Water varying. — 

 There are many ways of ascertaining the amount of car- 

 bonic acid in the air with great precision. An experimenter 

 may make any one of them perfect, if he will only continue 

 to use it until familiarity ensues. Lime-water may be used 

 according to Table V. 



Table V. — Neutralization with lime-water*. Capacity of 

 bottle, 50 ounces. 



Air at 0° C, and 760 millims. bar. 



Carbonic acid 



Quantity of 



Carbonic acid 



Quantity of 



in tlie air, 



lime-water 



in the air, 



lime-water 



per cent. 



required. 



per cent. 



required. 





grs. 





grs. 



0-03 



120 



0-15 



599 



0-04 



160 



0-20 



798 



0-05 



200 



0-25 



998 



o-o6 



239 



0-30 



1197 



0-07 



279 



0-40 



1596 



o-o8 



319 



0-50 



1995 



0-09 



359 



o-6o 



2394 



o-io 



399 



070 



2793 



o-ii 



439 



o-8o 



3192 



O'lZ 



479 



0-90 



3591 



0-13 



519 



I"00 



3990 



o'i4 



559 







* The lime-water used is the ordinary lime-water diluted with 9 volumes 

 of pure distilled and fresh boiled water. 



