1917] AGRICULTURAL CHEMISTRY — AGROTECHNY. 413 



have been found to be perfectly reliable and comparatively simple to manipulate 

 are described. 



A new type of extractor, J. B. McNaib {Jour. Indus, and Engin. Chem., 8 

 (1916), No. 9, p. 838, fig. 1). — An original type of extractor which has been used 

 successfully in extracting plant material with 86° Baum6 gasoline and its ma- 

 nipulation are described in detail. 



A comparison of the relative efficiency of laboratory reflux condensers, 

 M. V. DovEK and J. W. Marden {Jour. Indus, and Engin. Chem., 8 {1916), No. 

 9, pp. 83ji-836). — From a critical examination of the efficiency of various lengths 

 of Liebig, Allihn, spiral, Hopkins, Davies, and Friedrichs condensers it has 

 been demonstrated that in order to obtain comparable results the rate of drop 

 back of the liquid must be in approximately equal weights per second. For such 

 a condition it is necessary that the condenser tube be beveled so that the drop 

 returns from one point only. The rate of boiling has very marked influence 

 upon the efiiciency of the condenser, as well as the bore and the narrowing at 

 the tip or constriction anywhere in the tube. Such conditions tend to cause 

 choking and consequently disproportionate great loss. For low boiling liquids 

 the length of the condenser is a factor in its efficiency, e.specially in the Liebig 

 type. 



" In experiments where a long condenser can be conveniently used, the Liebig 

 seems to be preferable, because it is a much less costly condenser and can be 

 easily cleaned. Where a short condenser is required, the Friedrichs seems best. 

 The short Liebig or Allihn can be used to advantage only when the rate of con- 

 densation is not greater than from 2 to 3 drops per second, or when some means 

 is used, such as a glass-wool plug in the top of the condenser or a test tube 

 inverted over the top of the condenser, to prevent too rapid a carrying away of 

 the vapor by air currents." 



Extending the usefulness of a shaking machine, R. M. Chapin and J. M. 

 ScHAFFEK {Jour. Itidus. and Engin. Chem., 8 {1916), No. 10, pp. 921, 922, fig. 

 1). — The authors describe fittings which can be applied to a flask-shaking ma- 

 chine so that the machine can be used as a sieve shaker and a shaker for liquids 

 in various other forms of containers. 



Aeration method for ammonia, B. S. Davisson, E. R. Allen, and B. M. 

 Stubblefield {Jour. Indus, and Engin. Chem., 8 {1916), No. 10, pp. 896-899, fig. 

 1). — Experimental data are reported by the authors from the Ohio Experiment 

 Station which show that ammonia can be determined by aeration over mag- 

 nesium oxid. 



The Foliu tubes were found to be of little value at the rate of air flow (1,080 

 liters per hour) used in the experiments reported. For complete absorption of 

 the liberated ammonia an absorbing tower in which the air could be completely 

 scrul>bed while passing through the absorbent was necessary. A modified tower 

 with which complete absorption of rather large quantities of ammonia was 

 possible in 2.5 hours is described. 



The use of considerably smaller quantities of magnesium oxid than are com- 

 monly recommended was found to yield as satisfactory results. 



It is indicated that a standard method of measuring the rate of aeration 

 should be adopted so that results from various sources may be comparable. 



Does vanadium interfere with the determination of phosphorus in soils 

 when the phosphorus is weighed as magnesium pyrophosphate? R. A. 

 GoRTNEK and W. M. Shaw {Soil Sci., 2 {1916), No. 3, pp. 299-304). — A series 

 of pho.sphorus determinations, using soil solutions to which known amounts of 

 vanadium were added, the phosphorus being weighed as pyrophosphate after 

 stapding for 24 hours, are reported in detail. In no instance was any appre- 



