GIO EXPERIMENT STATION EECOKD. 



iu order to provide fiu abuudauco of small particles which readily pass into 

 solution; the contents of the syphon may be diluted with one-third its volume 

 of distilled water before filterinj?, and this will result in the formation of a 

 solution of approximately fiftieth-normal strength. 



" For a determination of acidity, or lime requirement, 10 to 20 gni. of the 

 soil is placed in a bottle of 500 to 1,000 cc. capacity together with 200 to 300 cc. 

 of the approximately fiftieth-normal solution of calcium bicarbonate, and the 

 air in the bottle is displaced by a current of carbon dioxid in order to insure 

 against possible precipitation of the calcium carbonate during the period of 

 determination. The bottle is tlien placed in a shaking machine for three hours, 

 after which time it is opened, the liquid is filtered, and a portion of the filtrate 

 equal to half of the original amount of bicarbonate solution is titrated against 

 tenth-normal acid, using methyl orange as indicator. The difference between 

 this final titration and that of the initial solution represents the amount of cal- 

 cium carbonate absorbed, each cubic centimeter of tenth-normal acid being 

 equal to 5 mg. calcium carbonate. 



" This method has been tested on a number of different soils, the behavior of 

 which has been ascertained bacteriologically and chemically in the laboratory. 

 A few of these results are summarized, in w^hich tlie production of ammonia 

 and nitrates and plant growth in untreated and limed soils is given. . . . 



" In addition to its value for practical agricultural work, the method will 

 possibly be of use iu various ecological pi'oblems, Avhere the relations between 

 plant and soil require more accurate determination." 



Method of determining- tlie lime requirement of soils, C. U. Jones {Aiiicr. 

 Fcrt., 39 (1913), No. 11, pp. 28, 29).— "Take 5.6 gm. soil, add 0.5 gm. calcium 

 acetate (tested reagent), place in a S-in. mortar, and mix with pestle. Add 

 sufficient water (room temperature) to make a fairly stiff paste. Pestle for 20 

 seconds, add. 30 cc. water, and continue mixing for 30 seconds. Wash into a 

 200-cc. flask, and keep bulk down to about 100 cc. Let stand, with occasional 

 shaking, for 15 minutes. Make up to bulk of 200 cc, mix, and filter through a 

 dry filter. Discard first 10 to 15 cc, which may be cloudy. Titrate 1(X> cc of 

 the clear filtrate, using pheuolphthaleiu as an indicator with decinormal NaOII. 

 This reading multiplied by 2 gives the cubic centimeters of decinormal alkali 

 required to neutralize the acetic acid in 200 cc. of the solution. This figure times 

 the factor l.S times 1,000 equals the pounds of lime (CaO) required i^er 2.000,000 

 lbs. of soil." The calculation may be shortened by multiplying the number of 

 cubic centimeters of decinormal sodium hydroxid used by 3,600. 



" The factor l.S is a tentative one only, it having been secured on a relatively 

 small number of samples representing Rhode Island. Massachusetts. Vermont, 

 and New Jersey soils. The method is extremely rapid, one man easily making 

 50 determinations in a day." 



See also a previous note, Loew (E. S. 11., 20, p. S15). 



A new method for the determination of soil acidity, E. Truog {Science, ii. 

 ser., 40 {1914), No. 1024, PP- 246-248).— One of the most serious drawbacks in 

 the study of soil acidity is the lack of a suitable qualitative and quantitative 

 method for its determination. While the litmus paper test when performed 

 properly is a fairly satisfactory qualitative test its reaction with carbonic acid 

 is confusing. With the view of securing a more reliable method the zinc suli^hid 

 test was devised, which depends upt>n the evolution of hydrogen sulphid when 

 acid soils are boiled with zinc suljihid and water. 



" Ten gm. of soil is placed in a 300 cc. Erlenmeyer flask and to this is added 

 1 gm. calcium chlorid, 0.1 gm. of zinc sulphid, and 100 cc. water. This is thor- 

 oughly shaken and then heated over a flame. After the contents have boiled one 



