OCTOBEE 2, 1914] 



SCIENCE 



493 



hydroehlorie acid wtieh readily liberates hydrogen 

 sulphide from zinc sulphide. 



This statement brings out very clearly the 

 absurdity of the position of those who accept 

 the humic acid theory. These humie acids 

 are supposed to be strong enough and soluble 

 enough to liberate hydrochloric acid from 

 calcium chloride, but not strong enough or 

 soluble enough to liberate hydrogen sulphide 

 from zinc sulphide. It is also suggested 

 that this method be made the basis for 

 a quantitative determination of the lime 

 requirement of the soil. The writer does not 

 believe this possible because he has shown* 

 that acid soils do not adsorb equivalent 

 amounts of different ions. A determination 

 of the amount of zinc adsorbed by the soil 

 will not teU. us the amount of lime to be ap- 

 plied to the soil. Furthermore it is not pos- 

 sible to use a factor to determine the amount 

 of lime to be used from the quantity of 

 hydrogen sulphide given off, because it has 

 been found that the ratio of the amounts of 

 two different ions adsorbed will vary with the 

 character of the soil used. The ratio of the 

 amount of zinc adsorbed to that of calcium 

 will vary with each different sample of soil 

 depending upon the kind of colloidal matter 

 present. The only sure way to determine the 

 lime requirement of an acid soil is to use the 

 same material in the test as is used in the 

 field for correcting the acidity. This is done 

 in the methods of Veitch and Siichting. 



As to the qualitative methods for the detec- 

 tion of soil acidity, it has been found that 

 all kinds of litmus paper are not suitable. 

 In fact, in the chemical laboratory of the 

 Michigan Agricultural Experiment Station, 

 Kahlbaum's litmus paper has been found to 

 be the only one not so thoroughly saturated 

 with alkali as to make it unsuitable for this 

 purpose. This litmus paper is so sensitive that 

 it is necessary to leave it in contact with the 

 soil particles only for a moment or two. In 

 this way it has been found that soils only 

 very slightly acid give a distinct test. 



J. E. Harris 



Division ae Chemistry, 

 Michigan Experiment Station 



*Loc. cit. 



A suggestion in connection with the 

 stark-ei/Ectric effect 



The discovery last year of the separation of 

 certain spectrum lines when emitted in an 

 electric field has been followed by a remark- 

 ably thorough investigation of the phenomenon 

 by Stark and his co-workers.-^ Hydrogen, 

 helium, lithium, calcium, sodium, magnesium, 

 aluminium, thallium and mercury lines have 

 been examined; but only the diffuse, subordi- 

 nate series lines of hydrogen, helium and 

 lithium show a separation as great as an 

 angstrom for a field intensity of 10,000 volts 

 per cm. The Stark-electric effect differs from 

 the Zeeman effect in that the various lines of 

 the same series are not equally affected, but, 

 for the same field, the separation increases 

 with the number of the term. Stark empha- 



I^G. 1. 



Heliuta r ; ^ 



„. Jioralfel 



+ - jKT^n^iciiIar' 



Fig. 2. 



sizes the complexity of the effect, and gives no 

 law for the relative separation of various lines 

 of the same series, though he suggests that a 

 relation should be sought between the relative 

 change of frequency of the various lines and 

 their term numbers.^ 



lAnnalen der Physilc, 43, 965-1047, 1914. 



2£. c, p. 1033. 



