514 Br. R. A. Smith on the Examination of Air. [Dec. 13, 



surprised at others clinging to it, even when imperfect ; but it is no less 

 important that I should give my experience. 



lor ordinary cases I obtain sufficiently accurate results by apparently 

 less exact measurements. With carbonic acid it may be possible to use 

 aspiration with good results, because this acid does not adhere to the 

 tubes ; and by an increase of bottles for absorption all may be safe ; but 

 the increase of absorbing vessels is troublesome. 



With salts and acids, such as hydrochloric and sulphuric, the difficulty 

 of absorption is not so great ; but the adherence to the tubes is remark- 

 able, and there is no hope of any good result without washing out the 

 tubes which give a passage to the air. 



With organic substances both the difficulties occur, adherence to the 

 tubes and passage through the solutions. I doubt if it is possible to 

 wash out the tubes sufficiently ; in such cases, the result is worse accord- 

 ing to the length of the passage. I have tried various ways to over- 

 come the difficulty, but have found only one way, and that is a very 

 laborious one. These points have long been known to me, and for some 

 time have been spoken of ; but I add a few results so as to impress them 

 on others. The importance of having a chemical department to our 

 observatories cannot be long overlooked. 



Bellows pump and shaking compared with aspiration and 

 rose-ended tubes. 



(Air at back of Devonshire Street, Manchester.) 



Aspiration. 



Volumes C0 2 per million Tolumes air. 



Experiment 1. 



1st bottle gave 89 



2nd „ 63 



3rd „ 58 



Total ,...210 in series of 3 bottles. 



Experiment 2. 



1st bottle gave 24 



2nd „ 15 



3rd „ 13 



Total 52 in series of 3 bottles. 



Experiment 3. 



1st bottle gave 52 



2nd „ 22 



3rd , 35 



Total 109 in series of 3 bottles. 



Experiment 4. 



1st bottle gave 41 



2nd „ 17 



3rd „ 53 



4th „ 35 



409 vols. C0 2 per million vols, air by 



shaking. Total 146 in series of 4 bottles. 



