UNIVERSITY OF CALIFORNIA PUBLICATIONS 
 
 IN 
 
 AGRICULTURAL SCIENCES 
 
 Vol. 3, No. 7, pp. 131-134 March 15, 1918 
 
 A NEW METHOD OF EXTRACTING THE 
 SOIL SOLUTION 
 
 (A Preliminary Communication) 
 
 BY 
 
 CHAS. B. LIPMAN 
 
 While studying, in 1914, some of the data obtained by Quincke 
 in measuring the forces by which thin water films are held by tiny 
 particles of solid matter, there occurred to the writer a new possibility 
 for a method of extracting the soil solution from soils with optimum 
 moisture contents. By making a simple calculation, I found that if 
 Quincke's figures were correct, particles of .005 mm. in diameter had 
 the power of holding very thin films of water with a force equivalent 
 to about 300,000 lbs. to the square inch. I argued, therefore, that 
 since particles of .005 mm. diameter constitute the "clay" fraction in 
 some mechanical analysis systems and since a large part of soil 
 material may consist of much larger particles, that it should be 
 possible to bring to bear on soils by pressure apparatus already in 
 existence enough force to separate soil particles from some water, 
 even when soils contained relatively small quantities of moisture. It 
 appeared to me, moreover, that the large machines used in engineering 
 laboratories for testing the strength of materials should be admirably 
 adapted to the task of expressing water from soil if suitable containers 
 for the soil are employed. With this idea as a basis, I started, in the 
 year above mentioned, to experiment first on peat soils with a letter 
 press of the old fashioned sort and found that water could be obtained 
 with it from peat containing 40% of moisture. I then proceeded to 
 have made a special perforated brass plate for the bottom of an iron 
 casing about 12 inches long and about 6 inches in diameter. A quan- 
 tity of clay adobe soil with optimum moisture content was placed in 
 
132 University of California Publications in Agricultural Sciences [Vol. 3 
 
 the tube, a plate placed over it and pressure applied in a machine of 
 a capacity of 200,000 lbs. to the square inch. About 25 c.c. of liquid 
 were thus obtained from eight pounds of soil. The result of this ex- 
 periment was unsatisfactory, owing to the small amount of liquid 
 obtained from a soil with an optimum moisture content. I determined, 
 therefore, to use a tube with a much smaller diameter (1 to 2 inches), 
 so that the pressure exerted by the machine could be concentrated 
 on as small a surface as possible and thus rendered more efficient. 
 When such a tube was made, other difficulties were encountered. A 
 few months later, these were surmounted and revised forms of appa- 
 ratus were thus prepared from time to time as other duties permitted. 
 No form of these was satisfactory even though I had demonstrated 
 that small amounts of the soil solution could be obtained with some 
 of them. During the last few months, however, I have had the privi- 
 lege of the counsel of Mr. C. T. Wiskocil of the Department of Civil 
 Engineering of this university, who has designed a new form of 
 pressure tube for my purposes. Such a tube was made up and we 
 have tried it out, recently, on several occasions with gratifying results. 
 In the case of a very fine sandy soil containing an optimum moisture 
 percentage (about 15% by weight), nearly two-thirds of the moisture 
 was expressed from samples of 300 to 400 grams of moist soil. In 
 the case of a clay loam soil, we were not so successful, but from two 
 or three samples of about 300 grams each of such a soil containing 
 about 20% of moisture (by weight), we obtained enough of the soil 
 solution to make conductivity measurements and, if needed, quanti- 
 tative analyses. Certain difficulties were encountered in pressing the 
 clay loam soil, which did not obtain in the case of the fine sand, but 
 these were also surmounted by another suggestion originating with 
 Mr. Wiskocil. Even now we find that our apparatus needs to be 
 changed, or a new one must be made to stand pressure in excess of 
 50,000 lbs. to the square inch, so that greater efficiency in pressing 
 clay loams and clays may be attained. The detailed description of 
 our apparatus, and of the results of conductivity measurements and 
 analyses of the solutions obtained are reserved for description in 
 another paper in which due credit will be given Mr. Wiskocil and 
 Dr. I). D. Way nick for invaluable assistance rendered in connection 
 with these matters. 
 
 My principal objed now is to direct the attention of my colleagues 
 in soil investigations <o the Fact that, after nearly four years of desul- 
 tory effort, I have succeeded in demonstrating that direct pressure 
 
1918] Lipman: A New Method of Extracting the Soil Solution 133 
 
 can be used successfully for purposes of obtaining the soil solution 
 as it exists in relatively thin films around the soil particles. The pro- 
 cedure is rapid, clean, and of high efficiency. With further improve- 
 ments in apparatus which we are now planning, the method should 
 supplant all other methods known today, including even the Morgan 
 procedure. 1 None of the other methods are really satisfactory and 
 even that of Morgan is laborious and slow, and introduces the factor 
 of oil, which complicates and renders it extremely time-consuming 
 and untidy. Within receut months, I have noted in the literature 
 that attempts have been made by Ramann, Marz, and Bauer 2 and by 
 Van Zyl 3 to use direct pressure as I have done. The original papers 
 detailing the work of these investigations are not available to me, 
 however, and I am almost entirely in the dark as to the details of 
 the method and, in one case, of the magnitude of the pressures em- 
 ployed. The maximum pressure thus far exerted in my method has 
 been approximately 53,000 lbs. to the square inch, whereas Ramann 
 and his associates with a hydraulic press seem to have used only about 
 1500 lbs. per square inch. Moreover", if the abstract of their paper 
 which is available to me has interpreted the authors correctly, their 
 method is only applicable to soils made up of very fine particles or 
 containing much organic matter. My experience has always been 
 that the coarsest soils are always the easiest to manage in expressing 
 water from them. Indeed, until recently, the fine grained soils, as 
 above intimated, gave me considerable trouble, because they would 
 creep out of the container in fine ribbons, while the pressure was 
 being applied. Mr. Wiskocil's suggestion of a thin casing of sand for 
 the fine grained loam or clay loam has obviated that difficulty, how- 
 ever. I judge from my experience, moreover, that Ramann and his 
 coworkers must have used very wet soil or they could not possibly 
 have secured solutions from them at the low pressure mentioned. The 
 abstract of Van Zyl's paper says nothing about the pressure used by 
 him and the manner in which it was applied. The statement is that 
 the soil can be "squeezed." Other comparisons of my method with 
 the comparable ones just discussed will be given in a later paper. 
 
 Finally, it may not be superfluous to emphasize the importance to 
 all soil studies of the proper use of the method which I have described 
 above. It allows of the direct determination of the concentration of 
 
 i Soil Science, vol. 3, p. 531 (1917). 
 
 2 Int. Mitteil. Boclenkunde, vol. 6, p. 27 (1916), cited from Chem. Abst., vol. 11, 
 no. 22, p. 3078 (1917). 
 
 3 Jour. Landw., vol. 64, p. 201 (1916), cited from E. S. E., vol. 36, p. 720. 
 
134 University of California Publications in Agricultural Sciences [Vol.3 
 
 the soil solution, and of the amounts of each of the solutes contained 
 therein. It renders possible, further, such studies as will clarify our 
 vision with regard to the relations, if any, which obtain between the 
 soil solution and soil extracts as ordinarily made. It permits us for 
 the first time, so far as I am aware, to obtain quickly and directly 
 large portions of the soil solution as it exists naturally under field 
 conditions when crops are growing, and thus to correlate these solu- 
 tions in all their qualities with the conditions of the growing crop. 
 It may doubtless be the means of throwing much light on the methods 
 for making nutrient solutions for growing plants, and probably also 
 on many obscure problems in plant physiological pathology. Indeed, 
 the possibilities are many in which the method which I have described 
 for obtaining the soil solution can be used to the very great advantage 
 of soil and plant studies. 
 
 Transmitted March 8, 1918.