Feb., 1 9 1 3
T H E JOUR!Y.4L OF I.\-DU.STRIAL
gram per 1000) and fill burette with ? \ i / 2 0 HC1. Take no account of A; or N / 2 0 acid used in the previous titration. Run in N / 2 0 HC1 until the lemon color of the alkaline methyl orange just darkens to slight orange,' take reading of N / z o acid and subtract blank, which should be about 4 cc. I cc. iV/20 HC1 = 0 . 0 0 2 2 gram CO,, 0 . 0 0 2 8 gram CaO or 0 . 0 0 5 gram CaCO,. CONCLUSIONS
which must of necessity attach t o an essential and very elusive element of plant food. While some plants may prefer t o take up nitrogen as ammonia there can be but little question as yet t h a t most plants prefer the nitrate, and we have further evidence that in the absence of such nitrate material the enforced absorption of ammonia by plants is apt to result in certain manifestations of disease due to the disturbance of their physiological mechanism. This, therefore, together with the fact which Hilgard has pointed out,' that uvthurnified organic matter, in his definition of the term, will not nitrify, would appear to invest the humus, determination in soils by some method similar to that of Grandeaul with primary importance in the chemical analysis of soils. Equal importance will, of course, attach to the nitrogen determination in humus since from what has been said above it is that, and not the total soil nitrogen, which may be depended upon t o yield through nitrification an available supply of nitrogen to plants. The general acceptance of the views above given has led t o the prosecution of extensive studies looking toward the perfection of the method for determining humus in soils and the reader is referred for a discussion thereof t o the recent work of Always and his associates and t o that of Kelley and M ~ G e o r g e . ~But while much work has been done on the method of determining humus, but little or no systematic work has been done on the determination of nitrogen in the humus since it has always been assumed t h a t the latest modifications of the Kjeldahl or Gunning method were as reliable for determining nitrogen in the humus as they were for determining that element in other substances. To obtain a more reliable and uniform method for this determination we have carried out a series of investigations in which some of the best known methods for the determination of nitrogen in humus were compared and the results of which we describe below.
The boiling of soils with mineral acids a t 100' C. (as pointed out b y Cameron, Marr and others) decomposes organic matter and liberates CO, which is not present as carbonates and therefore the official method is of no value as a measure of carbonates in soils. That if soils are boiled under reduced pressure a t 50' C. with very dilute mineral acids no organic matter is broken up and the CO, evolved is all derived from carbonates. That the litmus paper test, if properly made, is the best qualitative test we have for the presence or absence of native carbonates in soils from humid regions. That some soils may give alkaline aqueous solutions, not due t o the presence of carbonates but t o the hydrolysis of certain minerals which exist in these soils. That, although the reddening of blue litmus paper b y soils may be due t o the absorption of the base from the hydrolyzed litmus salt, the presence of native carljonates in a soil may either prevent this selective absorption or cause a n interchange of bases t o take place. That if a native carbonate, capable of being decomposed by weak HC1 a t low temperatures, is present in a soil it is indicathd by the bluing of red litmus paper when brought in contact with the moist soil. That if there are no alkalies or basic materials, in a soil, which are capable of giving alkaline solutions, the absence of such substances will be indicated b y the reddening of blue litmus paper. That if these conclusions are correct, as is strongly indicated by the data already presented, there exists HUMUS E M P L O Y E D I N THE EXPERIMENTS in soils which redden blue litmus paper a condition I n order to experiment with widely different kinds favorable to the formation of acids or acid salts which would unite with the base absorbed from hydrolyzed of humus we extracted soils of low, good, and very litmus and fail t o return another base in its stead, high humus content in accordance with the method thus producing the reddening of the indicator, even outlined in Circ. 6 , of the California Agricultural though it yields no H ions to a water solution. I t is Experiment Station. The soils employed for this therefore possible that such a soil may be capable purpose were as follows: of producing a physiological effect similar to that proN o . 1. Light sandy soil from walnut orchard, Anaheim, California. duced by stronger acids which do yield H ions t o Humus content 0 . 5 5 per cent. No. 2. Silty clay loam derived from the State of Washington. Humus aqueous solutions. content 8 .89 per cent. LABORATORY OF
THE
CHElllCAL
DEPARTMEW OF THE OHIO AGR.EXPT.STI.
No. 3. Tule soil from island in the Sacramento River. organic matter. Humus content 2 8 . 7 per cent. EXPERIMENTS
A CONTRIBUTION TO OUR METHODS OF DETERMINING NITROGEN I N HUMUS B Y CHARLESB . LIPMAZAND H . F. PRESSEY Received Sept. 30, 1912
So far as investigations on the subject have gone t o date, nitrogen as nitrates still retains the importance It will be well for those not familiar with this titration t o practice on solutions containing a little Na2C03. It will be necessary for each analyst t o establish and adhere strictly t o a constant end point for both indicators.
OS
THE
DETERMINATIOX
Searly all
O F NITROGEN
I N V A R I O U S H U M U S SOLUTIONS
Portions of fifty cubic centimeters of humus extract were boiled with one gram of magnesium oxide in 5 0 0 cc. Jena Kjeldahl digestion flasks until no more ammonia was given off as indicated by a test with 1 2
3 4
"Soils," Jfacmillan 8; Co., 1910. p. 359. Circ. 6, California -4gr. Expt. Station. Bzrll. 115, Nebraska rlgr. Expt. Station. B d l . 33, Hawaii Agr. Expt. Station.
I44
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
I. The Hibbard method of digestion gives the highest amounts of nitrogen in all cases except one (see Soil No. 3), thus showing a more thorough digestion. 11. The duplicate and triplicate determinations show the best agreement when the Hibbard method is employed. 111. The digestion is carried out most rapidly by the Hibbard method and, particularly, much more rapidly than by the salicylic acid method which, in other respects, comes the nearest t o the Hibbard method in yielding satisfactory results. IV. I n all the methods employed, considerable trouble with bumping was experienced except with
litmus paper. The residue was then treated for the digestion of the nitrogen b y the different methods whose relative efficiency was to be tested. All the methods given are so well known as t o need no further description here. The last method, which was first suggested by Hibbard, as a result of some of his investigations on fertilizers, deserves brief description here, however, since it was published only recently' andcbecause it has given by far the best results in our hands. The method of digestion as proposed by Hibbard consists in treating the substances t o be analyzed with 30 cc. of concentrated H,SO, until fumes of SO, begip to come. off. There is then COMPARISON OF
Method of N determination employed Wilfarth's method..
Gunning-Atterberg method..
NITROGEN DETERMINATIONS BY DIFFERENT METHODS Soil No. 1 soil NO. 2
Time necessary t o clear Nitrogen solution' found Minutes. Mg.
.......................
...............
25
{ 1143
20
Time necessary Per cent. to clear nitrogen solution in humus Minutes
.........................
3.91
30
4.86
4.40
25
5.32
5.89
20
5.57
30 5.44
added 1 2 grams of a salt mixture consisting of I O grams K,SO,, I gram FeSO, and 0.5 gram CuSO,, and the solution is digested until the nitrogen is all changed t o ammonia. There follow results obtained by the use of humus portions equivalent in the case of Soil No. I t o I O grams of the soil, in the case of Soil No. 2 t o 1 . 6 6 grams of the soil and in the case of the Soil No. 3 t o 0 . 5 gram of the soil. The amounts of nitrogen found in milligrams are given in duplicate or triplicate and the percentages of nitrogen are calculated on the basis of the averages of these amounts. All other data are given in the table below: I n a comparison of the data set forth in the above table, and the experience had in the management of the various determinations we find:
I
40
35
(3.33
Salicylic acid method.. ...........
Soil No. 3
Time necessary Per cent. to clear Nitrogen nitrogen in solution found humus Minutes Mg.
2.31
Hibbard method..
Feb., 1913
5.14
40
6o
{ { {
t
13.27 13.64 13.51 13.05 13.66 13.87 13.94 13.66 13.87 14.28 14.21 14.10
B y JOHNA. SCHAEFFER
The manufacture of sublimed white lead, the commercial name for the basic sulfate of lead prepared by the sublimation process, depends directly upon the oxidation of galena, the sulfide of lead, when subjected t o intense heat in a n oxidizing atmosphere. The combustion under these conditions proceeds with violence resulting in the formation of a white sublimate, which, when purified, is known as sublimed white lead. THIS JOURNAL, 2, 463. Paper presented at the Eighth International Congress of Applied Chemistry, New York, September, 1912. 1
2
4.62
4.71
4.82
4.95
the Hibbard method, in which ' the digestion proceeded rapidly and quietly in all cases, thus confirming the experience of Hibbard as reported in the paper above cited. V. The manipulation included in the Hibbard method surpasses in simplicity and speed all the other methods tested, among which are those most commonly used to-day. I n view of the fact, therefore, that the Hibbard method is far superior t o the others so far as both accuracy and speed are concerned, we must urge its use in all humus nitrogen determinations. SOIMRESEARCH LABORATORY O F CALIFORNIA UNIVERSITY BERKELEY
I
LABORATORY AND PLANT
THE MANUFACTURE AND PROPERTIES OF SUBLIMED WHITE LEAD*
Per cent. nitrogen in humus
The reaction which occurs in this oxidation of galena may be written as follows: 6PbS 1 1 0 , = 2Pb,S,O, 2S0,. This formula, Pb,S,O, or zPbSO,.PbO, is analogous t o the generally accepted formula for the basic carbonate of lead--zPbCO,.Pb(OH),. Commercial sublimed white lead, however, contains a higher percentage of lead sulfate than that required for the above theoretical formula. While the formation of the theoretical basic sulfate of lead is entirely feasible, its manufacture has not proved commercially advantageous. The conditions for the oxidation of the sulfide of lead are, consequently, so adjusted that a compound showing about 16 per cent. of lead oxide is ob-
+
+
