'694 REPORT— 1900. 



process for determining atmospheric carbonic anliydride is described by means 

 of which results of great iiccuracy may be obtained. Tims in the final set 

 of test experiments with artificial mixtures of purified air and carbonic anhydride 

 in known volumes a mean error (in six detertuinations) of about 1 per cent, of 

 the gas was found, corresponding with some four parts per million of air taken. 



For use by a scientific expedition it seemed, however, to the authors that a 

 different process is required in which the operations at the place of observation 

 should be as simple as possible, and of such a nature as to permit of the actual 

 determinatioDS being made at any convenient time later, when the resources of a 

 properly equipped laboratory are available 



The authors hive accordingly devised a method which fulfils these conditions, 

 and which is simple and accurate. On the one hand it resembles Pettenkofer's 

 process in that a relatively small volume of air is examined (about six litresj, 

 while, on the other, Miintz and Aubin's principle is adopted of absorbing the 

 carbonic anhydride by caustic potash solution and afterwards liberating it by 

 ebullition in. vacuo with an acid and measuring its volume in a suitable gas 

 analysis apparatus. 



A series of sealed tubes is prepared in the laboratory, each tube containing an 

 accurately measured volume of weak potash solution (the amount of combined 

 carbonic anhydride which such a solution always contains having been ascer- 

 tained for a given stock). 



The only operations which have to be performed at the place of observation are 

 the collection of the air sample in a suitable receiver : the transfer of the contents 

 of one of the sealed tubes to the latter, and after absorption of the atmospheric 

 carbonic anhydride their retransfer as far as possible to the same tube, which 

 will be again sealed. The tubes can of course be kept for an indefinite period both 

 before and after their contents have been thus treated, and the determination of 

 the absorbed carbonic anhydride made, when convenient, with an aliquot portion 

 of their contents. The experiments made to test the accuracy of the new method 

 were satisfactory. Artificial mixtures of purified air and carbonic anhydride in 

 definite volumes were employed (the two being in about the proportion they occur 

 in ordinary air). Five determinations in such mixtures gave a mean error of 

 1"3 per cent, of the carbonic anhydride taken equivalent to four parts per million 

 of air. 



3. On the Distribution of Chlorine in West Yorkshire. 

 By William Ackroyd, F.I.C. 



The present observations are to be regarded as the preliminaries to an attempt 

 to construct isochlors for this part of Yorkshire. The subject is one of acknow- 

 ledged importance. Professor Mason remarking: — 'State maps, such as those 

 issued for the States of Massachusetts and Connecticut, are most valuable, and th^ir 

 construction is well worth the expenditure of public money.' ^ Althougli the work 

 is not far enough advanced for map construction, the figures which follow, and 

 observations thereon, will be of chemical and hygienic interest during the visit of 

 the British Association to Bradford. 



In the first place these British normal chlorine figures are very high in com- 

 parison with the published American data. The lowest Massachusetts figure is 

 •07 part of CI per 100,000 in the area farthest removed from the Atlantic sea- 

 border : here the lowest found has been -7 part per 100,000 in the upper reaches 

 of the Wharf, and all round it appears that the Yorlcshire figures are about ten times 

 larger than those of the State of Massachusetts, which is to be accounted for — 

 (1) by the closeness of the sea-border on either side to the Pennine range, and (2) 

 by the density of population in and the antiquity of the inhabited areas. 



The unit isochlor area is coextensive with the highest hills and their becks, 

 deans and gills. The following chlorine determinations with waters from the 



\ W. P. Mason, Examination of Water, p. 29. 



I 



