ALUMINUM AND FERRIC HYDROXID6. 15 



acid than the distilled water culture. On testing for chlorin, after 

 the second cropping, it was shown that only mere traces of that ele- 

 ment were found in any of the solutions except Nos. 5 and 6, in which 

 potassium chlorid was used. Even in solutions 9 and 10, to which 10 

 parts per million of hydrochloric acid were originally added, only 

 traces of chlorin were found. The amounts of chlorin found in solu- 

 tions 5 and 6 after the second cropping were approximately 5 parts 

 per million on an average, or about one-seventh as much as was pres- 

 ent after the first crop was grown. In a similar test for sulphuric 

 acid in the various solutions it was shown that they all contained 

 appreciable amounts, but that solutions 7, 8, and 13, which had been 

 treated with potassium sulphate, contained about two to three times as 

 much sulphuric acid as the others. This acid was apparently either 

 not absorbed to the extent that the chlorin was or else was excreted 

 by the roots in a larger quantity. 



The weights of the roots in both crops and of the stems in the 

 second one,* when grown with lime, were much greater than when 

 grown without it. The weight of the residual seed, on the other 

 hand, was greater in the unlimed solutions, thus indicating that in 

 an alkaline medium the process of translocation of the seed constitu- 

 ents goes on more readily and completely than under the influence of 

 an acid reaction. , 



EXPERIMENTS USIN,G ALUMINUM AND FERRIC HYDROXIDS TO 

 REDUCE ACIDITY OF SOLUTION. 



A second series of experiments was made, using aluminum hydrate 

 instead of calcium carbonate to keep the solutions from becoming 

 acid. This aluminum hydrate was prepared from aluminum sul- 

 phate by precipitation with ammonium hydrate and was washed free 

 from impurities. It was not allowed to dry, but was added as a thick 

 cream. Carbon black was kept in all of the cultures as in the calcium 

 carbonate series. Plate V shows the effect of the aluminum hydrate 

 used instead of lime in the solutions containing potassium chlorid, 

 hydrochloric acid, potassium sulphate, and sulphuric acid. The 

 results after the plant had grown five da} 7 s indicate that many sub- 

 stances, which are capable of neutralizing the acid of the culture 

 medium and of keeping it alkaline, may be of benefit to the seedling. 



In Plate VI, figure , is shown the relative effect of the addition 

 of aluminum hydrate to solutions containing 150 parts per million 

 of sodium nitrate and 10 parts per million of sodium hydrate. 

 There is no difference between the two crops, and the aluminum 

 hydrate failed to produce any effect upon either. This indicates 

 that, at this stage of growth at least, the reaction of the solution is 

 of more importance than the added plant .foods. 



