456 Mr. W. Stiles and Dr. F. Kidd. Position of the 



(d) Ahiminiuvi Sulphate {Carrot). — With aluminium sulphate we are 

 dealing with a substance which is not toxic, but which gives unusual results 

 appearing at first sight similar to those obtained with toxic substances such 

 as copper sulphate. In view of these results (Table VI and fig. 4), it is necessary 

 to emphasize the marked absence of injurious action on the part of this salt 

 even in comparison with such relatively harmless substances as potassium 

 and sodium chlorides. If we take the more delicate potato tissue as a 

 standard, it is very noticeable how perfectly healthy the discs remain in 

 solutions of aluminium sulphate of all the strengths here used, in comparison 

 with similar discs in distilled water, or in solutions of sodium or potassium 

 chloride. 



With aluminium sulphate an increase in conductivity occurred in all 

 concentrations. The results, however, were irregular. The increase was less 

 in N/5000 aluminium sulphate than in distilled water. It was greater in 

 N/500, and greater again in N/50. The values in N/10, however, did not 

 show a still further increase, but fell below those obtained in N/50. These 

 irregularities do not appear to be due to experimental error, for exactly 

 similar results were obtained on repeating the experiments. It is to be borne 

 in mind also that all experiments were conducted in triplicate. 



It is difficult to draw definite conclusions from these results until further 

 analysis is made. For the present, our suggestion is that the aluminium ion 

 is absorbed and its place taken by hydrogen ions or some other ion, which 

 results in increasing the conductivity of the external solution. There are 

 three lines of evidence which support this view. In the first place, as will 

 be described in the second paper in this series, our experiments indicate that 

 the sulphates of non-toxic metals such as potassium or sodium are very little 

 absorbed in comparison with the chorides and nitrates. Since, as has been 

 said above, our conductivity measurements only indicate the absorption of 

 the least absorbed ion of a salt, this appears to show that the SO4 ion is not 

 easily absorbed. On the other hand, Meurer (3) has shown by direct analysis 

 of the external solution that the aluminium ion is ' readily absorbed from 

 aluminium sulphate solutions by carrot and other tissues. We quote his 

 figures below.* Lastly, the exosmosis which occurs from the discs when 

 subsequently returned to distilled water, as described in a succeeding section 



* Meurer's results for the absorption of aluminium by potato are as follows (for the 

 meaning of the expression absorption ratio, see at foot of next page) : — 



375 grs. carrot in 750 c.c. of a 0'54 per cent, solution of Al2(S04)3. 

 Estimation of AljOg in 50 c.c. before experiment, O'OSOO grs. 

 After two days 0'0623, absorption ratio 0'62. 

 After four days 0600, absorption ratio 0"73. 



