SOILS FERTILIZERS. 419 



pose several different processes of water and sewage purification are described 

 and illustrated, and the fundamental principles of their operation emphasized. 

 For the second purpose an exhaustive review of technical literature on the 

 subject is given, bringing out the most salient features developed. 



The g-ermicidal action of ultraviolet lig-ht in clear, turbid, and colored 

 water, M. Oker-Blom {Ztschr. Hyg. u. Infekiionskrank., 74 {191S), No. 2, pp. 

 W-247). — Investigations are reported on the practicability of water steriliza- 

 tion by ultraviolet light, in which the retarding action on the germicidal action 

 of the ultraviolet light of turbidity and coloring in the water within natural 

 limits was particularly tested. Bacillus coli communis, B. paratyphosis B, 

 Vibrio el-tor, and B. peptonificans served as test bacteria. 



In tests of a commercial drinking water sterilizer, with the water perfectly 

 clear and colorless, sterility with regard to the test bacteria was obtained when 

 the water passed through the apparatus at a speed of from 50 to 90 liters 

 (13.2 to 23.8 gals.) per hour, and had a bacterial content of about 10,000 per 

 cubic centimeter. The exact limits for the germicidal effect of the apparatus 

 relative to speed and bacterial content of the water were not established. No 

 great difference was observed in the resistance of the different test bacteria to 

 the germicidal action of the ultraviolet rays, but the water bacteria were more 

 resistant than the test bacteria. Clay turbidity reduced the germicidal effect 

 of the ultraviolet rays, but with a low turbidity the retarding action was small. 



Large quantities of peat extract coloring also reduced the germicidal action, 

 but weak mixtures had little retarding effect. Medium quantities of humus 

 substances in the treated water did not especially hinder germicidal action. 

 Barium sulphate turbidity and vesuvin coloring had little retarding effect A 

 bibliography is appended. 



SOIL&— FERTILIZERS. 



The effect of heat on Hawaiian soils, W. P. Kelley and W. McGeorge 

 (Hawaii Sta. Bui. SO, pp. 38). — In the investigations reported in this bulletin 12 

 different soils, representing a wide range of types and agricultural conditions, 

 were heated to 100 and 250° C. and to ignition, and the effect of these treat- 

 ments on the solubility in water and fifth-normal nitric acid of the mineral 

 constituents and on the form and loss of the soil nitrogen was studied. 



The results were variable, but in many cases there was an increase in the 

 solubility of the inorganic soil constituents as a result of heating. An important 

 exception was a decrease in solubility of lime and magnesia at the higher 

 temperatures and of iron at the lower temperatures. 



The solubility of the constituents of soils used in aquatic agriculture was 

 found to be abnormally high, but when these were dried this was not so pro- 

 nounced, and when such soils were heated after drying they were affected much 

 the same as dry-land soils. 



The conclusion is reached that no single factor is sufiicient to explain fully 

 the solubility effects resulting from heating. It is thought, however, that this 

 is due mainly to physical causes, more particularly to the action of the heat in 

 evaporating the water films surrounding soil particles which hold the soluble 

 matter under high pressure, thus leading the soluble constituents deposited on 

 the surface of the particles in condition to be more readily taken up when 

 water is again added. It is also recognized that heating may benefit soils by 

 Improving aeration. 



Heating to 200" C. or above caused a loss of approximately 25 per cent of 

 the total nitrogen of the soil, practically destroyed all nitrates, and stopped 

 nitrification, but it resulted in an abnormally large production of ammonia, 



