Jan., 1913
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
rious single salts and the antagonistic action of other salts in overcoming the toxicity, applies to conditions obtaining in solutions. Because the addition of ime exerts a strong antagonism in overcoming the toxicity of a solution of magnesia and vice uemu, it does not necessarily follow that such a n antagonistic action is exerted in ordinary soils. In ordinary soils it is probable that the ratio of the bases has no bearing on the fertility in the respect noted above, for the following reasons : I . The soil particles exert a physical effect in diminishing the toxicity of any salt solution. Jensen found that in quartz sand much higher concentrations of toxic salts were required to produce death than in water cultures.= 2 . The soil solution is a more or less balanced solution, containing a great variety of ions, and undissociated molecules.2 3. The soil solution, so far as we can determine, is a dilute solution. These acts, of course, do not apply to soils impregnated with alkali salts. In alkali soils we might expect to find the productivity influenced by the ratio of lime t o magnesia, as well as by the ratios of other bases,^ since in such soils we have relatively concentrated solutions of soluble salts. The experiments with soils in pot cultures to test the hypothesis have thus far given conflicting results. The method of these experiments has been to add the carbonates, sulphates, and chlorides of lime and magnesia to different soils to alter the lime-magnesia ratios. The pot experiments of Loew and his coworkers in Japan have apparently confirmed the theory.4 These experiments have been criticized on the ground that they were not always carried out in duplicate, that too few plants were grown, and t h a t the conclusions mere not always based on the relative weights of the plants but sometimes on the relative heights and number of branches.5 The pot experiments of Meyer6 and of Lemmermann, Einecke and Fischer,7 which are by far the most exhaustive on the subject, have given negative results. These have been criticized on the ground that too many plants were grown per pot and that insufficient fertilizer was supplied, 8 It should be borne in mind in judging these experiments that when large doses of the carbonates or oxides of lime and magnesia are added t o the soil, not only the ratio of lime t o magnesia is altered, but also the reaction of the soil. Since ground marble, ground magnesite, precipitated calcium carbonate and precipitated magnesium carbonate vary in the intensity S. H. Jensen, Bot. Gaz., 43, 11. How successive additions of various ions diminish the toxicity of a solution is shown IIY W. J . V. Osterhout, Bot. Gaz.. 44, 259. 3 Kearney and Cameron, LOC. cit. Vd. Reports in Vol. I., Nos. 1 and 2, of Agr. E x p t . Sta., Tokyo; also Vols. IV., V., VI., VII., of Col. of Agr., Tokyo Imp. Univ. 0. Lemmermann, et al., Landw. Yahrb., 11, Xos. 1-2. p. 177. D. Meyer, Land& Yahrb.. 1904, 3 7 1 : 39, 254 (1910) (Enganzungsband 111). 0 . Lemrnermann, A . Einecke, H. Fischer, Lartds. Yahrb., 4 0 , N o s .
'
1-2.
Loew, I b l d . , 42, 181 (1912).
35
of their action,' a mixture of ground marble and ground magnesite will induce a reaction different from that induced by either alone. It has been amply shown t h a t the reaction of a soil is one of the strongest factors in determining the growth of certain plants. Hence in the experiments where large amounts of lime and magnesium carbonates were applied to the soil the results in many cases may be attributed as well t o variations in the soil reaction as to variations in the lime-magnesia ratio. SUMMARY
The soil experiments to test directly the effect of the lime-magnesia ratio on the growth of plants have given conflicting results. This lack of' agreement may be due to the fact that some of the experiments were not properly carried o u t ; or it may be that the apparently confirmatory results arrived a t by some investigators are to be attributed rather to alterations in the soil reaction than to the lime-magnesia ratio. From the effect of salts on plants grown in water cultures we should not expect plants to be influenced by the ratio of the bases under the conditions obtaining in any but alkali soils. From field observations i t is certain that soils with an exceedingly wide ratio of lime to magnesia may be exceptionally fertile. Hence it would appear that in analyses of ordinary soils the ratio of lime to magnesia is of no significance, but in analyses of the soluble salts of alkali soils the ratio of lime to magnesia may be exceedingly important. PORT0
RICO.%GRICULTURAL
EXPERIM.IENT S T A T I O Y
>fAYAGUBZ
A PROPOSED MODIFICATION OF T H E OFFICIAL METHOD O F DETERMINING HUMUS B y 0. C. SMITH Received August 24, 1912
The determination of the humus content of soils
has always presented difficulties because of the inability to obtain a clear solution for evaporation. There have been several methods proposed but none of them have given very good satisfaction on all soils. By adding ammonium carbonate solution, a clear filtrate is obtained. By evaporating to dryness and again extracting with 4 per cent. ammonium hydroxide a clear solution is obtained, but this process is long and tedious and some of the humus is a p t to be occluded by the precipitate of clay. Other methods for obtaining clear solutions are by the use of a Pasteur filter, a centrifuge and a modified clay filter. The official method states that the 4 per cent. ammonium hydroxide solution should be shaken for the first twenty-four hours and then allowed to stand twelve hours and settle. The clearest part is then drawn off,filtered, and the determination made without any further treatment. This filtering does practically no good, and it is only very rarely that enough clear solution can be obtained in this way to make the determination satisfactorily. Our experience shows, however, that if the sediment is not allowed to settle, but is shaken well, and all of the soil possible is poured 1 D. Meyer, Landw. I'ahrb., 1904, 371 : also Kossovich and Althausen. E x p . Sta. Record, 23, 226.
36
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
onto the filter, a perfectly clear solution can easily be obtained. At first the filtrate is as turbid as that in the funnel. This may be returned to the filter or discarded ; but after about five or sixhours, the filtrate in most cases is clear. With soils running high in humus percentages, a clear filtrate can often be obtained in a n hour or two; while in clay, especially red clay soils, it may be twelve hours before the solution runs clear. But a clear solution is always obtained. I n determining the humus in over zoo soils, there was not one that did not give a perfectly clear filtrate and only one or two that took more than twelve hours. If the filtering is started in the morning, by night the filtrate is clear in most cases, and the next morning two or three hundred cc. will have filtered through perfectly clear. After the first two or three hundred cc. have run through, the filtering is generally very slow and t o prevent losses by evaporation the funnels are placed directly into Erlenmeyer flasks and covered by watch glasses. It has been found best to use five- or six-inch funnels and Schleicher and Schiill folded filters with hardened points, twenty-four or thirty cm. in diameter. With this size enough solution can be poured in a t once to run for four or five hours. Generally one filter full is all that is needed t o start a clear filtrate, but until this is obtained the filter should be kept nearly full so as to deposit a layer of soil over the entire paper. Several different papers and combinations of papers have been tried. On one set, S. & S. hardened was used for one of the duplicates and the ordinary S. & S. folded with hardened points for the other; using both of these on the same funnel was also tried; cheap papers did not give as good results although a clear solution was obtained. The double papers or the hardened did not give a clear filtrate any sooner than the folded and the filtration was much slower. Any first-class paper is all right if it is strong enough t o hold the three to five hundred cc. of solution that is put on it. By using this method of obtaining a clear filtrate i t is very seldom that the duplicates do not check t o within one-tenth of one per cent. Below is a fair sample of the results obtained:
Lab. No. 108-5-23 108-5-25 108-5-27 108-5-30 108-5-36 108-5-55
Weight of soil used, 10 grams: aliquot taken, one-fifth Dish and Dish after Loss on humus dry ignition ignition Humus Grams Grams Gram Pet cent. 47.1325 47.1186 0.0139 0.70 0.0125 0.63 49.0290 49.0165 49.0508 49 ,0431 0.0077 0.39 48.0067 47.9987 0.0080 '0.40 38.9278 38.9163 0.0115 0.58 39.5477 39.5358 0.0119 0.60 50.3218 50.3036 0.0182 0.91 49.0553 49.0378 0.0175 0.88 49.5910 49.5615 0.0295 1.48 48.9532 48.9253 0.0279 1.40 48.3436 48.3012 0.0425 2.13 47.3165 47.2732 0.0433 2.17
A comparison of this method was made with the Mooers and Hampton method and the Rather method. The last two methods were run a t a previous time by Chemist No. I of this laboratory. I n his work a lower result was obtained for the Rather method in nearly
Jan., 1 9 1 3
every case. The author took the same soils and determined the humus by the Rather and simple filtration methods. Chemist No. 3, also of this laboratory, determined the humus by the latter only. The solutions were prepared according to the Official method by washing with one per cent. hydrochloric acid and water and digesting with four per cent. ammonium hydroxide fortwenty-fourhours. At the end of the digestion, a filter full was taken from the flask and the remainder set aside t o stand twelve hours and settle for the Rather method. At the end of this time, 130 cc. of the solution were decanted through a filter and 0.6 5 0 gram of ammonium carbonate was added and shaken when dissolved. This solution was again allowed t o stand twelve hours and settle, when i t was again decanted through a filter, I O O cc. were evaporated, dried five hours a t rooo, weighed, ignited and again weighed. This took forty-eight hours from the time the four per cent. ammonium hydroxide was added until the solution was ready for evaporation. With the Smith method, the filtering was started as soon as the soil had digested twenty-four hours. Three hours afterwards, the filtrate was clear and a t the end of twelve hours, 2 0 0 cc. of clear solution had run through. From this, roo cc. were drawn and the drying and ignition made exactly a s in the Rather method. By this method i t was thirty-six hours from the time ammonium hydroxide was added until the solution was ready for evaporation, thus gaining twelve hours: 130 cc. of the clear filtrate by the latter method were taken immediately after drawing the sample for the analysis and 0.650 gram of ammonium carbonate was added. These solutions were treated exactly as the Rather method solutions were and a t the end of twenty-four hours there was no sign of a precipitate, in any case. All of the filtrates were compared as to color and in every case the solution obtained by simple filtration was richer in color than that obtained by the Rather method. This color was evidently taken from the solution in the Rather method by the action of the ammonium carbonate or by the heavy flocculent precipitate. However, the ammonium carbonate did not have any effect on this color when the solution was obtained clear by simple filtration. METHODS FOR T H E DETERMINATION O F HUMUS MooersSmith Hampton Rather Rather Smith method method method method method Chemist Chemist No. 1 Chemist No.2 No. 3
COMPARISON OF
. A 1 -_h-c _ _
70
%
%
%
%
%
%
%
%
%
Lab. No. humus ash humus ash humus ash humus ash humus ash 12-1-110 1.478 1.14 1.175 0.38 1.545 0.228 1.498 0.448 1.568 2.16 12-1-111 0,700 0.64 0.470 0.34 0.560 0.230 0.693 0.490 0.773 1.278 12-1-115 0.660 0.54 0.343 0.26 0.558 0.208 0.708 0.750 0.773 1.358 12-1-117 0,523 . . 0,310 .. 0,478 0,158 0.440 0.478 0.528 1.073 12-1-120 1.275 .. 1.063 .. 1.348 0,218 1.363 0.700 1.485 2.340 12-1-122 1,093 .. 0.775 0.933 0,168 0.845 0.585 0.988 1.580 12-1-123 0,458 0,325 0.408 0.200 0.438 0.665 0.528 1.470 . 1.498 1,705 0,300 1.803 0.793 1.880 2.620 12-1-142 1.740 0,895 0.898 0,160 0.980 0.918 1.030 1.770 12-1-143 1,073 Average 1.000 . 0.761 . 0,937 .. . 0.974 .. . 1.061 .
.. . .. .
.. .. .. .. .
..
It will be observed from the above table that in every case the percentage of ash is larger in the Smith method than in the Rather method (both run by Chemist No. 2) but the percentage of humus is
The preliminary work showed that the calcium was the constituent removed with the greatest difficulty and therefore might serve as an index to all of the other mineral constituents. The factors which i t seemed necessary to determine may be outlined as fol1on-s:I . The time necessary to remove the lime by. (a) digestion of ash with acid over steam, ( b ) boiling the ash with acid on a hot plate. 2 . The comparison of the efficiency of dilute and concentrated acid. ( I t nTas finally concluded t o use concentrated hydrochloric acid, concentrated nitric acid and dilute hydrochloric ac d of specific gravity r.11.1 This dilution is made by mixing equal parts of concentrated hydrochloric acid and water.) 3. The determination of which acid (nitric or hydrochloric) is most efficient. 4. The effect of dilute sodium hydroxide to break up silicates not decomposed by acid. 5 . The efficiency of moist combustion as compared with ordinary combustion. The feces were ground to a fine powder when dry and preserved in air-tight bottles. A large portion of the powdered sample was ashed t o a cream white ash and preserved for analysis. The moist combustions were conducted in Kjeldahl SUMMARY flasks, the boiling of the ash was conducted in Erlenmeyer flasks and the digestions were made in beakers, I . The weighing out of a n exact amount of amall of which were made of standard glass. Watch monium carbonate is not necessary. glass covers (on the beakers) and test tubes of water 2. The time taken for the determination is shorter (suspended in the flasks) acted as condensers, and in most cases. prevented loss of acid by evaporation. 3. Nothing is added that could precipitate part of the humus. After treatment with acid, the sample was diluted 4. It seems to give more uniform results. to twice its volume t o prevent the acid from attacking DEPARTMENT O F AGRICULTURAL CHEMISTRY the filter paper, and the sample was filtered and washed. UNIVERSITY OF MISSOURI The filtrate was then evaporated to dryness. The COLUMBIA silica residue was taken up with dilute acid, filtered and n-ashed. This filtrate was made up to volume for THE DETERMINATION OF LIME I N COW FECES' analysis. B y R . ADAMSDUTCHER Sliquots were made alkaline with ammonium hyReceived June S . 1912 While conducting the analytical work on the ash droxide and brought back to faint acidity with acetic of cow feces, in a mineral nutrition experiment, it was acid. After boiling a few seconds, the insoluble found that the results were not concordant. This is phosphates were filtered off and washed thoroughly. due to the fact that the ash of COTV eces runs abThe calcium was then precipitated as the oxalate normally high. The ash content of the feces used in and determined with N/ j o potassium permanganate this investigation was 2 0 . j j per cent.: while Dr. P. F. in the usual manner. Trowbridge,Z of the Missouri Experiment Station, has The following data shoxs (I) that the lime is refound the ash to run as high as 39 per cent. This moved in a shorter period of time when the ash is unusually high ash content is due to the large amount boiled with acid than \?-hen it is digested over stcam. of sand, dirt, etc., that the cow receives nTith the feed. ( 2 ) That the ash must be boiled three hours to inMethods of ash analysis are very lax with reference sure complete removal of the lime. (3) That in t o the acid treatment of the ash. The time varies digestion, concentrated acid is more efficient than from I O minutes3 boiling with acid, for plant ash; t h e acid diluted I : I . (4) That when boiled, the t o I O hours4 digestion over steam, for soils. concentrated acid has no advantages over the weaker As nothing could be found relating to the ash of acid. cow feces, i t was decided to determine the factors which When the acid is incapable of breaking up the influenced the removal of the mineral constituents. silicates, it is advisable to treat the large silica residue ' Abstract of thesis suhmitted in partial fulfilment for Degree of Mas- with sodium hydroxide as proposed by the Freseniuster of Arts, Cniversity of Xlissouri, 1912. Will method.' When these alkaline washings are Private communication. nearly the same, the greatest difference being 0.15 per cent. in 12-1-115. I t will also be seen t h a t there is a variation in the results of the two different men using the same soils and Rather method, being a difference of 0.37 per cent. in soil 12-1-110. I n only one soil, 12-1-143, do the results agree. This seems to indicate that if the exact amount of ammonium carbonate is not added each time and the solutions do not have exactly the same treatment, different results are obtained. The per cent. of humus obtained by Chemist No. 3 was slightly higher than that obtained by Chemist h-0. 2 ; also the per cent. of ash was higher. But this is easily explained by the fact that this determination was the first time Chemist No. 3 had used this method. The solutions from which he drew his aliquot gave a slight deposit of clay on standing. He did not allow the filtrate to become perfectly clear before he took the portion for the determination. I n our routine analyses, we allowed about fifty of these solutions t o stand two weeks and at the end of t h a t time only two or three showed any precipitate at all. The greatest difference between the results of the two men doing the proposed method is 0 . 1 4 per cent. in soil 12-1-122, notwithstanding the fact that one of the men had never used the method before.
"Food Inspection and Analysis," Leach, p. 303. Bullefin 107, Official and Provisional Methods, U. S. Dept. of Agriculture.
* This is t h e strength of acid used in soil analysis (BzLU 107, U. S. Dept. of Agriculture). 2 Jour. I . Gasbeleuchtung, 49, 853 (1906).
