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sulfite a correction of 0.10cc. N / I O iodine per 2 0 0 cc. filtrate. Incidentally it may be noted t h a t we have here t h e basis for a good practical method for estimating thiosulfate i n t h e presence of sulfite. If, as t h e writer believes, t h e combined determination of mono-sulfur a n d poly-sulfur as described constitutes a method for t h e estimation of sulfide sulfur which is more accurate in practice t h a n a n y other previous method, i t is obviously impossible t o check t h e accuracy of t h e new nlethod b y comparing i t s results with those afforded b y other methods. B u t such a comparison is of importance for practical reasons a n d has been undertaken. EXPERIMENT 3-Taking t h e standard method' of t h e A. 0. A. C. as a basis, procedure was modified in accordance with facts regarding t h e estimation of sulfuric acid a s barium sulfate brought out b y Allen a n d Johnston12 a n d b y Walter Allen a n d B i ~ h o p . ~Using I O cc. of t h e diluted sample, sulfide sulfur was separated b y ammoniacal zinc in t h e usual way. Next followed digestion with I O cc. N X I O caustic potash, adding water as needed, oxidation with hydrogen peroxide a n d strong acidification with 2 5 cc. concentrated hydrochloric acid. T o remove chlorates4 a n d silica-which must necessarily be present from t h e action of alkali on glass-the solution was evaporated t o dryness a n d t h e residue was heated several hours at 105 t o 110'' C. It was t h e n t a k e n u p with hot water a n d 5 cc. concent r a t e d hydrochloric acid, a n d t h e filtered solution, after cooling a n d diluting t o about 700 cc., was precipitated cold with a j per cent solution of barium chloride through a capillary t u b e according t o t h e procedure of Walter Allen a n d Bishop. T h e next d a y t h e precipitate was filtered on paper, cautiously ashed in a platinum crucible a n d ignited for 30 min. in t h e covered crucible over a No. 3 M6ker burner. T o determine t h e value of t h e factor S/BaS04 under these conditions, 2 j cc. of N / 2 sulfuric acid were precipitated after t h e addition of hydrochloric acid only, a n d after t h e addition of I O cc. of N X I O caustic potash, acidification, evaporation, etc., as in t h e method of analysis, a n d this factor was used in calculating t h e results. T h e trace of sulfur derived from t h e reagents was determined a n d allowed for in all t h e work. All operations were performed in duplicate. T h e samples were made after different formulas in connection with another investigation. T h e y were diluted a n d analyzed, using t h e gravimetric method for sulfide sulfur, I t o 3 days after preparation. For t h e determination of t h e poly-sulfur figure t h e dilutions unfortunately were not made until between 8 t o I O weeks later, t h e concentrates being preserved meanwhile in well-filled a n d well-sealed bottles. It is not desired t o discuss a t t h e present time changes which may occur in lime-sulfur solutions during storage, b u t it is necessary t o give here t h e results for thiosulfate sulfur also. 1 2 3
Bur. of Chem., Bull. 163, p. 70. J . Am. Chem. SOC.,82 (1910),588. Proc. 8th Intern. Congr. Appl. Chem., 1 (1912), p . 33. Compare Ramsay, J . Agr. Sci., 6 (1914), 194.
341
T h e results obtained appear in Table I, expressed as percentages of t h e diluted samples.
Sample A.. B..
... . ... . .. .. .,
C ......... D ..... . ...
E..,. . . . . .
TABLEI-RESULTS IN PERCENTAGES FIRSTDILUTION SECONDDILUTION Thiosul- Sulfide S Thiosul- Sulfide S fate S Gravimetric Sum fate S Volumetric Stim 0.387 1.622 2.009 0.378 1.644 2.022
0.458 0.453 0.418 0.444
1.674 1.755 1.801
1.790
2.132 2.208 2.219 2.234
0.445 0.443 0.408 0.440
1.744 1.815 1.839 1.819
2.189 2.258 2.247 2.259
The volumetric method for sulfide sulfur gave distinctly higher results in all cases, t h e actual differences varying from 0.022 per cent t o 0.070 per cent. B u t i t is evident t h a t t h e thiosulfate sulfur decreased slightly during storage in all cases. If it is permissible t o assume t h a t some thiosulfate sulfur h a d become changed t o sulfide sulfur, a n d comparison is made between t h e sums of t h e t w o forms of sulfur, t h e volumetric method still gives t h e higher results in all cases, t h e actual differences varying from 0.011per cent t o 0.057 per cent. The parallelism indicates a greater fault in t h e factors employed for calculating t h e results t h a n in t h e rationale of either method, a n d since t h e factor S / B a S 0 4 is purely empirical under t h e conditions of t h e gravimetric method t h e probability of error rests there. No experiments have been performed upon t h e applicability of t h e method t o use dipping baths contaminated with filth from animals. CONCLUSIONS
Methods are now available for estimating iodometrically t h e three important forms of sulfur in limesulfur solutions; thiosulfate sulfur, mono-sulfur a n d poly-sulfur, thiosulfate being t h e substance directly titrated in each case. The methods appear theoretically sound a n d practically applicable. The use of a single standard solution which can be so easily a n d accurately prepared a n d used as N / I Oiodine means a possibility of increased accuracy, as well as a saving of time, over t h e gravimetric estimation of sulfur as barium sulfate under conditions which demand t h e employment of a n empirical factor. BIOCHEMIC DIVISION,BUREAUOF ANIMALINDUSTRY, DEPARTMGNT OF AGRICULTURE, WASHINGTON
A NEW APPARATUS FOR THE DETERMINATION OF SOIL CARBONATES AND NEW METHODS FOR THE DETERMINATION OF SOIL ACIDITY' B y E. TRUOG Received October 29, 1915
I n recent years a number of methods a n d forms of a p p a r a t u s have been devised for t h e determination of soil carbonates and acidity. The present paper makes no a t t e m p t t o discuss in detail t h e methods a n d apparatus which have been devised a h d advocated. T h e apparatus here described is the result of a n a t t e m p t t o devise a form which embodies simplicity, ease of operation a n d accuracy of results. I n these respects it is believed t o have certain marked advantages. 1 Published with the permission of the Director of the Wisconsin Experiment Station. The writer is greatly indebted to G P. Wolf, T I,. O'Hora and A. H. Neumann for assistance in trying out the apparatus and methods.
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SOIL CARBONATE DETERMISATIOK
The old method of heating with strong acid a t boiling temperature t o decompose t h e carbonates has been largely abandoned in recent years, due t o t h e action of t h e boiling acid on organic matter with consequent liberation of C o t , causing high results. T o overcome this, Marrl used weak HC1 and boiled at j o o C. with reduced pressure, under which conditions he found t h a t t h e C O z obtained is practically all derived from carbonates. Gaither2 confirmed hiarr's results, a n d also devised an ingenious apparatus3 for carrying out t h e determination. MacIntire4 and Willis devised a method in which the carbonates are decomposed by J , I; H 3 P 0 4 , a t room temperature. Lately: in order t o be assured of complete carbonate decomposition, t h e y have replaced the I / I j with 1 / 1 0 HC1 and in t h e case of soils high in carbonates j They s t a t e t h a t the action of recommend ~ / HC1. I 'IO HC1 on soil organic matter a t room temperature 1s negligible on ordinary charges of average soil. Due t o its simplicity this method has certain advantages
530CE
FIG.
I--A
S E W FORM OF A P P A R A T U S F O R T H E DETERMINATIOX OF S O I L CARBONATES A X D SOILACIDITY
over the Marr method. ,A disadvantage in the method as operated by hlacIntire and Willis is t h a t t h e soilcontaining vessel has t o be agitated either b y hand or motor. I n order to overcome this difficulty and also make t h e titration of t h e e.i-olved COZ simpler and more accurate, t h e writer has devised t h e new form of apparatus shown in Fig. I. THE S E T V APPARATTUS
DESCRIPTION--The apparatus shown in Fig. 1 consists of a n evolution bulb, J , a wash bottle, W , and a n absorption tower. A . The evolution bulb J consists of a 300 cc. dropping funnel with t h e s t e m bent as shown. T h e f n e l y ground soil or other material is placed in this bulb with t h e acid solution. On 1
J O U Y .Agu. Sci., S (1908). 155.
2
THIS J O U R X A L , 5 (1913), 138.
3 4
I b i d . , 4 (1912), 611. Tenn. Agric. Expt. Sta., Bd1. 100
5
THIS J O U R N A L , 7 (1915), 2 2 7 .
Vol. 8,KO. 4
aspirating, t h e air enters through P and rises from t h e narrow neck of t h e bulb, effecting an efficient agitation of t h e soil and solution, thus eliminating t h e necessity of shaking, as is t h e case with t h e apparatus of MacIntire and Willis. A rather wide-mouthed dropping funnel should be selected in order t o take at least a No. 3 stopper. The sides of t h e funnel should slope uniformly t o t h e outlet in t h e stopper and should not leave a considerable shoulder around t h e outlet of t h e stopper on which soil may rest. The wash bottle W containing AgS04 is inserted t o remove HCl when this acid is used t o decompose the carbonates. T h e absorption tower is similar t o the one previously d'escribed in detail b y the writer.' Its advantages have been fully stated. It makes possible t h e use of Ba(OH)z as well as alkali hydroxides as a n absorbing medium for both slam- and rapid aspirations of low and high amounts of COz. Contamination from. the air is eliminated and washing is reduced t o a minimum. Y E T H O D O F OPERATIOS-A finely ground sample of I g. t o 2 j g. of soil, depending on the amount of carbonates present, is placed in t h e evolution bulb with jo C C . of w,ater. Fifty cc. of I / j HC1 are poured into the funnel I . Forty cc. of 0 . 4 -V Ba(OH)2 are run into the dropping funnel E . The soda lime tube is quickly replaced and t h e funnel is attached t o t h e tower. -After making the proper connections t h e whole apparatus is freed of COS by aspirating. I n starting t h e aspiration the suction should always be turned on before stop-cock S is opened in order t o prevent soil passing through the stop-cock. With continual aspiration and stop-cock S only slightly opened, t h e B a ( O H ) ? is allowed t o run out of t h e funnel E into the tower and then t h e stop-cock of E is closed. The soda lime tube is removed and 40 t o j o cc. of Cos-free water are quickly poured into t h e funnel and t h e soda lime t u b e is replaced. This water is now allowed t o r u n into t h e tower, thus washing the funnel practically free of Ra(OH)2when t h e stop-cock of E is again closed. The suction draws the absorbing solution u p into t h e tower. T h e HC1 is allowed t o run out of I into J , t o decompose t h e soil carbonates. After aspirating 30 min., slowly for the first L O min. followed b y more rapid passage, the COz is usually completely liberated and absorbed in the tower. When t h e decomposition and absorption are complete, t h e suction is closed off with a pinch-cock or stop-cock, and t h e stop-cock of E is gradually opened, allowing COz-free air t o enter, when the absorbing solution settles into the flask. The flask is next disconnected from the CO, source, and t h e n after t h e solution has fully settled into t h e flask, t h e stop-cock of E is closed. The tower is washed out as directed2in a previous article and the excess of Ba(0H)Z is immediately titrated with 0 . 4 N HC1. The amount of C O S is obtained b y difference. PRECACTIONS-If soil is allowed t o set in t h e eT0lUtion bulb for sometime without aspiration, it will THIS JOURNAL, 7 (1915). 1045. Regarding further details in t h e preparation of reagents, use O f various kinds of beads and operation of tower, see previous article in THIS J O U R N A L , 7 (1915). 1045. 1
2
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stick t o t h e sides a n d it is t h e n necessary t o shake t h e bulb until it becomes loosened. T h e stop-cock S should be adjusted so as t o secure a slight vacuum in t h e bulb J , in which case t h e air expands on entering, resulting in a violent agitation of t h e soil a n d a more rapid liberation a n d removal of Cos. With proper manipulation, a moderately rapid current of air suffices t o keep all t h e soil, if finely powdered, in rapid motion. With proper adjustment of stop-cocks, there is no trouble in soil passing through stop-cock S. According t o t h e preceding directions, t h e soil is treated with 1 / 1 0 strength HC1. Stronger HC1 u p t o I / S strength has been used with little apparent objection. A further s t u d y is being made of t h e strength of HC1 which suffices t o decompose t h e carbonates a n d minimizes t h e liberation of C o s from organic matter. SOIL ACIDITY DETERMINATIOK
343
methods for detecting a n d determining them. If soil acids were comparatively soluble in water, soil acidity would never be a serious problem in soils having good drainage, since t h e acids would be carried away in t h e drainage watFr. Because of their insolubility, it is necessary t o use soluble reagents in their detection a n d determination. This feature has been recognized in a new test1 devised b y the writer for t h e detection a n d determination of t h e degree of active soil acidity. This test is designed for practical work a n d i t indicates more satisfactorily t h e urgency of t h e need of lime a n d amount t o be used under field conditions t h a n a n absolute quantitative method. However, for research regarding t h e nature of soil acidity a n d related problems, a n absolute quantitative method is of great value. For this reason t h e following methods have been devised: PROPOSED
METHOD
FOR
ACTIVE
SOIL
ACIDITY~
PRINCIPLE-The principle of t h e method is as folA great many methods have been proposed for t h e determination of soil acidity. I n several of these lows: T h e soil is treated with a n excess of Ba(OH)2; methods t h e soil is treated with a neutral salt solution a current of COZ is passed in, changing t h e excess t o a n d t h e resulting acid extract is titrated. Since t h e carbonate, a n d after evaporation, a carbonate dereaction of salt solution a n d soil acids is one of equil- termination gives t h e excess, from which t h e amount ibrium (competition between acid of salt used a n d soil required t o neutralize t h e acidity is calculated. M E T H O D OF OPERATIOw-The soil is prepared b y acids) t h e titration does not indicate t h e total acidity a n d necessitates t h e use of a factor. I n advocating passing t h e sandy ones through a 2 0 mesh and t h e t h e same factor for all soils, t h e bold assumption others through a I O O mesh sieve. Samples are t a k e n has t o be made t h a t t h e acids in all soils are of t h e same as follows: of sands and sandy loams, 2 j g.; of silts, strength. T h a t this is not t r u e will be shown later. clays, a n d loams, 2 0 g . ; a n d of peats a n d mucks, 2 I , l 2 g. Since soil acids are quite insoluble, methods de- The soil is placed in a casserole, 3 5 cc. of water are pending on t h e liberation of COZ from solid CaC03 added a n d t h e soil is stirred till thoroughly moistened. cannot be expected t o prove satisfactory since this Gentle heating aids greatly in moistening peats. requires a reaction between two rather insoluble Fifteen cc. of 0.4 N Ba(OH)2 are added a n d allowed materials which, necessarily, is slow. Methods which de- t o act with constant stirring for just one minute, a n d pend on boiling t h e soil with a n excess of Ba(OH)2 then a moderately rapid current of C 0 2 is immediately a n d a n ammonium salt are open t o serious objection passed in for about two minutes with continued because practically all solutions of ammonium salts stirring, changing t h e excess of B a ( O H ) 2 t o t h e carwhen boiled give a n alkaline distillate a n d a n acid bonate. -4 little phenolphthalein may be added residue. T h e method of Veitch,' in which is determined t o indicate t h e point of complete carbonation, which t h e amount of C a ( O H ) 2 t h a t must be added t o t h e is best observed b y t h e disappearance of t h e color soil t o make t h e boiled water extract alkaline t o phenol- around t h e edges. ilfter evaporating immediately phthalein, also has certain objections as follows: t o complete dryness on a steam or water b a t h , never T h e method is long a n d tedious. The end-point varies with a free flame, t h e soil is transferred t o t h e evoluaccording t o t h e period of contact a n d amount of tion bulb of t h e soil carbonate apparatus a n d t h e C 0 2 shaking, due t o hydrolysis of neutralized substances. determined, from which t h e Ba(OH)2 required t o T h e method never determines t h e total acidity, b u t neutralize t h e acidity is calculated. For carbonate simply indicates a certain point of equilibrium of a n decomposition 1/15 H3P04 is used in place of t h e HC1 hydrolysis reaction between t h e water applied and used for soil carbonates. I n the case of coarse, s a n d y t h e various salts in t h e soil. ,411 of t h e methods just soils, t h e evolution bulb should be shaken occasionally described have been o f value in t h a t t h e results in- t o get all t h e material in motion. With t h e most dicate in a comparative way t h e degree of acidity. strongly acid soils, t h e amount of Ba(OH), applied None of t h e m , however, indicate t h e absolute a m o u n t t o t h e soil should be increased t o about 2 0 cc. t o of acidity as has sometimes been assumed. Lately, neutralize the acidity. The use of Ba(OH)2 is preHutchinson a n d MacLennan2 a n d also MacIntire3 ferred t o other hydrates because it is easily prepared have described methods in which a solution of C a C 0 3 Cos-free and t h e same stock solution also serves in carbonated water is used. T h e former claim t h e for use in t h e absorbing tower. For titration 0.4 LV HC1 is used. By using t h e weights of soil samples results correspond closely t o cultural practice. The insoluble n a t u r e of t h e soil acids must be and strength of B a ( O H ) 2 indicated, a n d assuming clearly recognized in a n y a t t e m p t t o devise satisfactory t h a t t h e weight of a n acre, 8 in. layer of sandy soil, is 2.,500,000 lbs. (clays, silts a n d loams 2,000,000 1 J. A m Chem Soc , 24 (1902). 1120. 2 3
Chem. News, 1914, p. 2854 THISJOURNAL, 7 (1915), 864.
1
2
Wis Agric. Expt. Sta., Bull. 249. Science, 42 (1915), 505.
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344
T'ol. 8, NO. 4
lbs., a n d peats
joo,ooo lbs.), t h e calculation of t h e acidity in terms of C a C 0 3 is greatly simplified. Under
t o acidity are added and then water, making t h e final volume 150 cc. The mixture is boiled for 30 min., TABLE I-ACTIVE SOILACIDITY I ~ Y Cc. OF 0.4 9 SOLUTION PER SAMPLE evaporated t o dryness on a steam bath and heated ( O R T O X S CaCOs PER ACRE), ON U S I N G HYDRATES INDICATED(a) for 2 ' i 2 hrs. a t 110' C. in an oven. About jo cc. KINDOF S O I L No. Ba(0H)z XaOH Ca(OH)% Sand ... . . . . . . . . . . , . . 1 of water are added, and COZ is run in t o carbonate 3.8 3.5 3.7 Sandy loam. , . . . . . , , , . 2 6.2 7.9 6.5 t h e excess of Ba(OH)2. After evaporation carbonates Silt loam.. , . , . , , , , , 3 6.3 6.4 5.2 Silt loam.. . . . . . . , , . 4 8.5 9.1 I . , are determined as before, from which t h e total acidity Peat... . . . . . , . , . . , , , 5 11.2 11.5 11.3 P e a t . . , . . . . " . .. . , , , 6 5.6 5.6 5.3 is calculated. The total acidity minus t h e active (a) Results for peat calculated to 5 g. sample. gives t h e latent acidity. these conditions t h e number of cc. of Ba(OH)2 used DIscussIoN-The latent acidity is usually t w o t o t o neutralize t h e acidity of t h e sample also represents three times t h e active. By repeating t h e boiling t h e tons of C a C 0 3 required per acre except with peats . and evaporation of Ba(OH), with t h e soil, t h e result where t h e result is in half tons. If other weights is usually increased slightly. On t h e soils studied, are assumed then the samples should be chosen accord- t h e results have been nearly t h e same whether NaOH ingly. Correction for moisture is made by using per or Ba(OH)2 was used. T h e method for latent acidity cent dry weight as divisor. Duplicates should check is being further studied and t h e procedure given is within 0.2 cc. not final. Latent soil acidity is undoubtedly much D I S C U S S I O N O F RESULTS-In Table 1 are given a less injurious t h a n active. The strength or avidity of ferv of the results secured b y this method and also t h e active acids is a very important matter and t h e results when t h e Ba(OH):! applied t o t h e soil is ref21 placed b y equivalent amounts of Ca(OH)2 and NaOH. T h e results are several times as great as are obtained with the Veitch method. The close concordance of results when different hydrates are used indicates clearly t h a t t h e method proposed measures a rather definite part of the acidity in soils. This acidity may be called t h e active a c i d i t y , since it combines instantly with bases t h a t are brought in contact. If the period 7 of contact of hydrate and soil is prolonged considerably Data oxw one minute, the results show a slow b u t gradual 7 h e CC. So/. rise up t o a certain limit beyond which no more base is taken up. By heating and evaporating before carbonating this reaction is hastened. This part of T t h e acidity which reacts only after continued contact may be called t h e i,rtactive or latent acidity. The total amount of latent acidity is usually several times t h a t of t h e active. T h e existence of active and latent acidity may be shown in another way by treating an acid soil for varying periods with a neutral salt solution preferably a n acetate, and titrating t h e acid P I G . 11-ACTIVE A N D LATENT S O I L ACIDITY A S INDICATED B Y . 4 C l D I T Y extract. Extracts secured after pt contact of one OF EXTRACT IN Cc. N / 2 5 SOLUTION AFTER VARIOUSPERIODS OF minute show a certain acidity which is very large in CONTACT BSTWEEX ACETATESOLUTION A N D SOIL comparison with t h e additional acidity indicated after a contact of many hours and even days. After one method for active acidity also makes possible a method minute contact, t h e rise is slow, h u t gradual, indicating for avidity of t h e active acids. t h e coming into play of the latent acidity. P R O P O S E D METHOD F O R A V I D I T Y O F A C T I V E S O I L A C I D S I n Fig. I1 are given t h e results obtained b y shaking By avidity of a n acid is meant its competing power 20 g. samples of acid silt loam soil with I j o cc. of for a base in comparison with another acid taken as a Ar sodium acetate solution (neutral) for t h e periods standard. In order t o determine avidity, i t is then indicated. T h e solutions were quickly filtered with only necessary t o determine t h e distribution between a Buchner funnel and titrated with X / 2 5 XaOH. equivalent amounts of the unknown and standard The existence of active and latent soil acidity is clearly acids, of a quantity of base just sufficient t o neutralize indicated. Prom other d a t a , although inconclusive, one of t h e acids. It is comparatively easy t o determine it appears t h a t in upland soils, t h e active acidity is the relative avidity of the active acids in different d u e largely t o acid silicates, and the latent acidity soils, if t h e amount of active acidity is known. t o a peculiar condition of kaolinite and allied comUETHOD-TO a sample of soil which is z1/2 times t h e pounds. weight of t h e one used for active acidity determina, ,
,
ll
f
PROPOSED
METHOD
FOR
LATENT
SOIL
ACIDITY
(PROVISIONAL) METHOD-A j g. sample (in case of peats 21/2 g.) is placed in a casserole or other suitable vessel, moistened with water, I O t o 20 cc. of 0 . 4 N Ba(OH)* according
tion. is added a I;O cc. solution of potassium acetate which contains a n amount of KC2H302 equivalent to t h e active acids in t h e soil sample. This solution is conveniently made b y taking t h e same number of cc. of neutral X KC2H302as there was used of 0.4 N
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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
B a ( O H ) z t o neutralize t h e active acidity, a n d diluting i t t o I jo cc. with COz-free water. The soil a n d acetate solution are vigorously shaken together i n a 300 cc. flask for t w o minutes a n d t h e n quickly filtered on a Buchner funnel a n d titrated with N/2j N a O H using phenolphthalein. Calculations are made as follows: Let a = avidity of acetic acid (conveniently taken as 1000) b = cc. i V / 2 j N a O H required b y titration c = cc. N K C 2 H 3 0 2used x = relative avidity of active soil acids (average of all) Then: x = ab/ 2 jc- b , and b y substitution of known values, x is solved for. Since soil acids are quite insoluble compared t o acetic acid, t h e relation between t h e figure obtained for avidity of soil acids a n d t h a t taken for acetic acid (1000) does not represent t h e strength of t h e active soil acids compared t o acetic acid. However, since t h e acids in different soils are practically all insoluble, t h e avidity figures for different soils are comparable. G E N E R A L DIscussIox-In Table 11 are given a few values of avidity secured b y this method together with t h e active acidity in tons per acre of CaC03 as measured b y t h e method described in this article, a n d also t h e degree of active crop-injurious acidity as measured b y t h e new test previously described. It is clearly evident t h a t t h e avidity of t h e active soil acids in different soils varies greatly, from which i t must be concluded t h a t t h e seriousness of a soil's acidity a n d t h e urgency of t h e need of lime are not indicated by t h e total active acidity alone. It is necessary t o also consider t h e avidity of t h e active acids. Soil 7 , for example, is much higher in t o t a l active acids t h a n No. 6, yet in cultural practice No. 6 responds decidedly t o liming a n d No. 7 does not. What is t h e explanation? I t is clearly a matter of avidity, since t h e avidity figure for No. 6 is nearly 8 times t h a t of No. 7 . From this i t is evident t h a t a n y practical method for t h e determination of t h e urTABLE 11-AMOUNT OF ACTIVES O I L ACID%AVIDITY OF ACTIVESOIL ACIDS, DEGREEOF CROP-IXJURIOUS ACIDITYIN SEVERALSOILS Degree of Active Acidity Avidity Crop-Injurious in tons CaCOs of Acidity by KIND OF SOIL N o Der acre Active Acids New Test Silt loam.. . . . . 1 72 4.9 Slight to Medium Silt loam.. . . . , 2 42 3.1 Very Slight Silt loam.. . . . . 3 96 9.3 Medium to Strong Clay. . . . . . . . . , 4 6.6 152 Very Strong Sand ... . , . . . . , 5 1.2 26 Very Slight Sand.. , . . . . . . , 3.4 113 Strong P e a t . , . , . .... , . 5.6 15 Very Slight AND
P
gency as t o t h e need of lime must t a k e into account both t h e q u a n t i t y a n d t h e quality (strength) of t h e soil acids. T h a t t h e new simple test for acidity actually does this is evident from Table 11. The degree of acidity indicated b y this test is t h e resultant of two factors, viz., quantity a n d strength of active soil acids which may conveniently be called t h e degree of crop-injurious acidity. Because of this feature, i t is superior t o a n absolute quantitative method in indicating t h e seriousness of t h e acidity and t h e advisability of using a light, medium or heavy application of lime. Because of t h e varying needs of different crops, t h e enormous yearly loss of lime through
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leaching, a n d t h e great complexity of soil acidity a n d related phenomena, it is ridiculous t o advocate methods for practical purposes which are said t o indicate down t o hundreds of pounds per acre t h e amount of lime which a farmer should use. An approximation in tons or perhaps half tons is t h e best t h a t can be expected a n d all t h a t is necessary. However, a n a b solute quantitative method is of t h e greatest value as a n aid in many lines of research on soils., Since nearly equivalent amounts of different hydrates are required, as shown b y Table I, t h e intervention of a t r u e chemical reaction is indicated, a n d i t may safely be accepted t h a t soil acidity is due t o true acids a n d not selective ion adsorption b y colloids a n d other adsorbing substances, as often stated. The reason t h a t N a O H sometimes gives a slightly higher result a n d C a ( O H ) 2 a slightly lower result t h a n Ba(OH), is undoubtedly due t o side reactions, such as action on organic matter, latent acidity, etc., which clearly would be different for t h e different hydrates. For a further discussion regarding nature of soil acidity see previous publication.' T h e enormous supply of latent acid substances in many soils of t h e humid region as indicated b y these methods is of t h e greatest importance in preventing excessive losses of bases b y leaching. It also offers a further explanation why MacIntirelZ Hardy a n d Willis were able t o secure large decompositions of MgC03 when this material was left in contact with soil t h a t supposedly had been completely neutralized. A more detailed paper regarding t h e nature of soil acidity is in preparation. S C M 41A R Y
I-A
new form of apparatus for t h e determination of soil carbonates is described. I t has certain marked advantages. 11-Evidence is given indicating t h e existence of two kinds of soil acidity, which are conveniently called active a n d latent soil acidity. 111-Methods are proposed for t h e determination of active a n d latent soil acidity, a n d also t h e average avidity of t h e active soil acids. IV-Data are given indicating as follows: Soil acidity is due t o t r u e acids a n d not selective ion adsorption b y colloids; t h e avidity of t h e active acids in differe n t soils varies greatly, which is of prime importance; a n d t h e new test for soil acidity previously described gives a more reliable indication as t o t h e seriousness of t h e acidity t h a n a n absolute quantitative method. DEPARTMENT OF SOILS. WISCONSIN EXPERIMENT STATION UNIVERSITY O F \%'ISCONSIN, MADISON
THE COMPARISON AND IDENTIFICATION OF VARIOUS TYPES OF SMOKING OPIUM3 By FRANK D. SIMONS Received November 29. 1915
DESCRIPTIVE
Smoking opium may be classified, according t o t h e method of preparation, as t h e product obtained b y : Science 42 (1915), 5 0 5 . Tenn. Agric. Expt. Sta., Bull. 107. a Published b y permission of the Secretary of the Treasury and the U. S. Appraisers of Merchandise, Baltimore. Md. 1
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