490 



EXPERIMENT STATION EECOED. 



I Vol. 37 



Intelligent use of road oil reduces maintenance, T. R. Agg {Etigin. News- 

 Rec, 78 (1917), No. 8, pp. 412, 41S. figs. 4).— It is pointed out tliat the use of road 

 oil is of little actual value unless good drainage is provided. All soils are 

 benefited, but under Iowa conditions the gumbos give the best results. 



Colorimetric test for organic impurities in sands, D. A. Abrams and O. E. 

 HarliEr (Struct. Materials Research Lab. [Lewis Inst], Circ. 1 (1917), pp. 7; 

 nbs. in Engin. and Contract., 47 (1917), No. 12, pp. 273). — A detailed descrip- 

 tion of the field and laboratory methods for the colorimetric test for organic 

 impurities in sand. 



"A sample of sand is digested at ordinary temperature in a solution of sodium 

 hydroxid (NaOH). If the sand contains certain organic materials, thought 

 to be largely of a humus nature, the filtered solution resulting from this treat- 

 ment will be found to be of a color ranging from light yellow up through the 

 reds to that which appears almost black. The depth of color has been found 

 to furnish a measure of the effect of the impurities on the strength of mortars 

 made from such sands. The depth of color may be measured by comparison 

 with proper color standards." 



Effect of water-on the strength of concrete, D. A. Abrams (Concrete High- 

 way Mag.. 1 (1917), No. 4. PP- 5-7, fig. 1; abs. in Engin. and Contract., 47 (1917), 

 No. 18, pp. 422, 423, fig. 1; Engin. News-Rec, 78 (1917), No. 4, p. 206, fig. ]).— 

 'I'he results of compression tests on 6 by 12 In. concrete cylinders made in mixes 

 ranging from 1 part cement and 9 parts aggregate to 1 part cement and 2 

 parts aggregate by volume are summarized. 



"These tests show that the effect of proportional changes in the mixing water 

 is approximately the same for all mixes of concrete. . . . The amount of 

 water which gives the maximum strength in concrete produces a mix which 

 is too stiff for most purposes." The following table, based on the experime-nts, 

 is given to indicate the approximate quantities of water which should be use*! 

 for mixes commonly employe<l iu concrete road construction: 



Concrete road mixtures. 



Bearings for agricultural machinery, V. W. Page (Amer. Thresherman, 19 

 {1917), Nos. 9, pp. 44-46. figs. S: 10. pp. 16-Ii<. figs. 4).— This is a discussion of 

 •he design and purpose of bearings for agricultura! machinery. 



Review of mechanical cultivation. M. Kingki.mann (liul. Snc. Encour. Indus. 

 Nat. [Paris], 127 (1917), No. 1, pp. 197-218. figs. 75).— This is a review of the 

 status of mechanical cu1tivati«m in Europe, with .special reference to war- 

 time conditions. Typical tests of dilTerent outfits are discusseil. 



A press for the Georgia carrier, M. A. Blake and H. C. Haink.s (New Jersey 

 Slas. Circ. 64 (1917), pp. 8, figs. 4)- — This circular describes and diagram- 



