February, 1927
INDUSTRIAL AND ENGINEERING CHEMISTRY
to volume a t 20" C. introduces an error of only 0.4 per cent of the gelatin present. To make sure that the gelatin is all in the soluble form we hold a t a temperature slightly above 35" C. for some time before polarizing. By adhering strictly to the quantities given in our modification of the Ferris method the calculation becomes very much simplified. The percentage of gelatin is obtained by simply substituting the weight of the serum for the volume in the original formula. But as the weight of sample is 200 grams and the specific rotation of commercial gelatin is 117, the only variables become the polariscope reading ( R ) and the weight of serum (bV), hence: Per cent gelatin = 0.00074 X R X W
For the estimation of gelatin by nitrogen, in the final solution, the procedure is similar, using the Ferris formula, but the factor 6.75 instead of 5.55. Ferris does not direct any correction for the nitrogen not due to gelatin in the filtrate. We have found from 2 to 3 mg. of nitrogen in 25 cc. of the final solution in blank determinations containing no gelatin. That the filtrate actually does contain proteins other than gelatin is shown by the invariable appearance of a beautiful violet color (tryptophane reaction: as soon as the sulfuric acid is added for digestion. Pure gelatins get yellow, but never show violet. Per cent gelatin = 0.135 X N X W
in which N is mg. of nitrogen in 25 cc. of the solution, and W the weight of serum.
269
Modified M e t h o d Into a tared 400-cc. beaker weigh 200 grams of the melted and thoroughly mixed sample. Add 25 cc. of water and enough hematoxylin indicator to color the sample distinctly pink. Heat t o 40" C. and titrate with 10 per cent acetic acid until the pink color has completely disappeared. Return the beaker to the balance and add water until the weight of the contents reaches 250 grams. Accuracy of 0.5 gram is sufficient. Mix thoroughly and return to the 40" C. water bath until the curd has fully separated. Filter through a small bag of cotton or linen. Weigh out 100 grams of the filtrate, add 3 cc. of a saturated solution of potassium alum, then 200 cc. of 95 per cent alcohol, with stirring. Cooling hastens the separation of the precipitate. Filter by suction on a 9-cm. filter, using a Biichner funnel. Tear up the paper and place in water in a small beaker. Soak until the gelatin has an opportunity to swell. Then place the beaker in warm water for half an hour, first adding water t o approximately 50 cc. Bring rapidly to incipient boiling and filter a t once into a 100-cc. volumetric flask, washing with hot water until the flask is nearly full. Allow the flask to cool to near room temperature, make t o the mark, and mix. The polarization can be made a t once, using a jacketed tube. Circulate water, which has been heated, through the jacket until a thermometer placed in the tubulature reads 40". Then shut off the water, allow the tube to cool to 35", and read. If the flasks are not read a t once they should be heated in a water bath a t 35-40" C. for half an hour or more before placing in the polariscope tube. The weight of serum to be used as a basis in calculating is obtained by subtracting the weight of fat and casein in 200 grams of the sample from 250 grams. Using a 200-mm. tube for polarizing, the per cent of gelatin is given by 0.00074 X R X W. Determine nitrogen in 25 cc. of the solution, deducting 2 mg. for the blank, and expressing the result in milligrams of nitrogen in the 25 cc. The percentage of gelatin is then found by 0.135 X N X W.
Determination of Mineral Nitrogen in Fertilizers' By C . H. Jones VERMONT AGRICULTURAL EXPERIMENT STATION, BURLINGTON, VT.
HE present official methods used in fertilizer analysis
T
was present. The following procedure for the determination of ammoniacal and nitrate nitrogen in fertilizers containing calcium cyanamide, urea, etc., has given very satisfactory results thus far in this laboratory. Method
to determine mineral nitrogen do not give true values when certain organic ammoniates are present. This condition is most marked when cyanamide is a component of the mixture. The value of calcium cyanamide as a source of nitrogen for plant growth is well recognized and its use in the trade well established. It is classed as organic nitrogen and if used by the manufacturer of commercial fertilizers it is but fair to all concerned that the analyst have at his disposal methods that will enable him to distinguish between mineral and organic sources of nitrogen. When the present official methods for nitrate nitrogen mere formulated, cyanamide and urea were not commercial sources of fertilizer nitrogen and their effect on the procedures adopted mas not considered. This may be of little moment where no attention is paid to the different forms of nitrogen present in a fertilizer, but if the manufacturer is required by law to guarantee mineral and organic nitrogen percentages, confusion may arise if the true nitrate content is not determined. Many states place a varying value on the nitrogen in fertilizers based on the form in which it is present. As a rule organic nitrogen is given a higher valuation than the mineral forms. These considerations prompted the writer to attempt to modify the existing official methods so that reliable results for nitrate nitrogen might be secured in present-day fertilizer mixtures, particularly when calcium cyanamide
Test the fertilizer qualitatively for nitrates. If present, proceed as follows: (I) PREPARATION OF ~OLUTIoN-~~ace 4 grams of the sample in a small beaker (150 cc.), add about 40 cc. of water, stir, filter by decantation, and after all the residue is transferred t o the filter wash to just under bulk of 200 cc., letting each washing run through before another is added. Make to bulk of 200 cc., mix, and treat three aliquots of 50 cc. each a s directed under (11) and (111). Or Place 4 grams of the sample in a 200-cc. flask. Add 160 cc. of water, shake thoroughly for 5 minutes, make to bulk of 200 cc., mix, and filter. (11) A>IMONIACAL NITROGEN-PlBCe 50 CC. (eqtlivalent to 1 gram) of the solution prepared according to (I) in a 500-600-cc. Kjeldahl distillation flask, add 150 cc. of water and 5 grams of magnesium oxide (heavy). Connect with an upright condenser, distil 100 cc. of the liquid into a measured quantity of standard acid, and titrate with standard alkali using cochineal or methyl red indicator. (111) NITRATEKITROGEN-(A) Place 50 cc. of the sample prepared according to (I) in a 500-600-cc. Kjeldahl distillation flask, add 10 to 12 perforated glass beads (3 to 5 mm.), 2 grams of reduced iron, and 10 cc. of dilute sulfuric acid (1:l). Rotate slowly and when any violence of reaction has moderated, place on hot plate and boil gently for 5 minutes. Remove, add 40 cc. of water, and cool. Add 100 cc. of strong sodium hydroxide solution. * Connect at once with a n upright condenser by means
1 Presented before the Division of Fertillzer Chemistry at the 72nd Meeting of the American Chemical Society, Philadelphia, Pa., September 5 t o 11, 1926.
The concentrated soda solution used is prepared by dissolving 525 grams 01 flake sodium hydroxide in 1 quart of water. I t should test close to 42' Be. a t room temperature.
*
INDUSTRIAL A N D ENGINEERING CHEMISTRY
270
of a Kjeldahl connecting bulb, and boil until 150 to 160 cc. have distilled over, and the distillate as it drops from the condenser shows neutral t o litmus paper. Collect the ammonia in a measured quantity of standard acid and titrate with standard alkali using cochineal or methyl red indicator. The nitrogen obtained represents that from nitrates, ammonia salts, and other nitrogenous compounds, proteins, cyanamide, urea, etc., that have been changed, wholly or partially, to ammonia by this treatment. (B) Correction Blank. Place 50 cc. of the sample prepared according to (I) in a 500-600-cc. Kjeldahl distillation flask and proceed exactly as under (A), except that no reduced iron is added. The nitrogen obtained represents that from ammonia salts and other nitrogenous compounds-proteins, cyanamide, urea, etc.-that have been changed, wholly or partially to ammonia by this treatment. The percentage of nitrogen obtained by procedure (A) minus that obtained by procedure (B) equals the percentage of nitrogen from nitrates contained in the sample.
Discussion of Results
Table I1 shows results secured by both the proposed and the official reduced iron methods and also indicates the amount and nature of the nitrogen present in each sample. A glance at the nitrate nitrogen percentages obtained on the first eight samples by the proposed method and the present reduced iron method shows a close agreement with theory in the case of the former, while the latter gives large increases. The 0.39 per cent against a calculated 0.25 per cent in sample K is the greatest deviation noted by the new procedure, and this is insignificant when compared with the 0.98 per cent secured by the official method on the same sample. Table 111
Caution. When cyanamide is present in amountsgreaterthan 150 pounds per ton or the distillate under (111-A)or (B)fails to show neutral when finally tested with litmus paper, repeat procedures (A) and (B)using a 25-cc. aliquot (0.5 gram) and add 25 cc. of water previous to the addition of the 10 cc. of sulfuric acid ( 1 : l ) .
NITROGEF:
SAMPLE
1 2 3
A critical study of. this method indicates that its success depends on securing a proper correction blank (B). This, it is plain, must very closely offset' any change due to the evolution of hydrogen other than its action on the nitrate present. For this reason the concentrated soda solution was employed. The results in Table I illustrate this point.
Vf 4
I'I 5
116
7
Table I NAOH
Cc.
Cc.
25
50
100
75 50 0
25 100
75 0
(B)
Per cent Per cent Sample H 3.16 1.54 2.70 3.68 3.54 4.10 Sample J 0.81 3.33 2.03 4.07
zztzN 1.62 0.98 0.56
0.5 0.5 0.5
2.52 2.04
2.0 2.0
1
2 3
1
2 3
10
1 2 3
11
Per cent
1 2 3
1:
12
THEORY
Percent
1
Nitrate nitrogen
Nitrate nitrogen
Per cent Per cent Per cent Nitrogen f r o m Cyanamide O n l y 0.77 0.74 0.03 1.12 1.05 0.07 1.51 1.40 0.11 Nitrogen f r o m Urea Only 0.98 0.98 0 1.68 1.75 0 2.74 2.77 0 Xitrogen f r o m Animal Tankage On13 0.14 0.21 0 0.21 0.18 0.03 0.21 0 0.21 Nitrogen from Coltonseed Meal Only 0.11 0.07 0.04 0.11 0.07 0.04 0.11 0.14 0
Per cent
(A)
(B)
_
_
REDUCED IKOH ~IETHOD
PROPOSED METHOD
EQUIVALENT Per cent
General Observations
(A)
~
I
Run procedures (4) and (B) synchronously and see that both aliquots are taken from the same solution.
CONCD.+ H20
T'ol. 19, s o . 2
0.56 1.12 1,65 0.07 0.10 0.14 0.07 0.10 0.Oi 0.07 0.10 0.17
I n the last two columns attention is called to the good agreement obtained by the magnesium oxide procedure on an aliquot of the water-soluble portion of the samples with results by the official ammoniacal nitrogen method. The last four samples are included to illustrate the effect of small additions of calcium cyanamide and urea to a mixture, the nitrogen in which was derived from nitrate of soda, ammonium sulfate, and animal tankage. Note the marked increase in apparent nitrate nitrogen shown by the reduced iron method in samples DD2 and DD3. Sample DD indicates that the proposed method is equally useful whether or not cyanamide is present. Table I11 shows the (A) and (B) procedures will give results that agree closely on fertilizers containing no nitrate nitrogen. The samples in Table I11 were made from acid phosphate and muriate of potash mixtures to which cyanamide, urea,
The addition of perforated glass beads insures gentle boiling, free from bumping, and no frothing has thus far been observed. From 50 minutes to 1 hour is usually required for the distillation of (A) and (B), and the flasks had best rest on asbestos-coated wire gauze. At the completion of the process add water to the flasks before cooling to prevent caking. I n making the solution of the sample it is simply necessary to dissolve all the nitrate and ammoniacal salts present. The amount of nitrogen from tankage, cyanamide, etc., that remains undissolved is unimportant.
Table I1
FERTILIZERS C O N T A I N I N G ACIDP H O S P H A T E
AND KCL, W I T H NITROGEN I N P E R C E N T S I N D I C A T E D , FROM:
Sample
L
x K
0
F
H
L DD DD1 DD' DDs
Nitrate of Calcium soda cyanamide
Urea
Tankage
Per cent Per cent Per cent Per cent Per cent 0 1.0 0 0.5 1.0 0 0.7 0 1.0 1.5 0.5 0.75 1.5 0 0.25 0.25 1.0 0 0.25 0.25 0.5 1.0 0.5 1.0 1.0 1 .o 1.o 1.0 2.0 0.5 2.0 1.0 1.0 0.5 0.75 0.5 1.0 0.5 0.25 1.0 1.0 0 0 1.0 1.0 50 grams D D 0 . 5 gram urea 50 grams D D 2.5 grams cyanamide 50 mams D D 1.25 grams cyanamide -k 0 . 2 5 Pram ufea
+ + +
REDUCED IRON
PROPOSED SIETHOD
(4)
Per cent 2.35 2.95 1.93 0.81 2.74 4.10 4.0i 2.03 2.10 2.46 2.67 2.33
(B) Per cent 1.26 1.40 1.54 0.56 1.65 3.54 2.03 1.44 1.09 1.44 1.61 1.33
MRTHOD
Nitrate nitrogen
Qitrate Amrnoniaca ,itcogen and nitrate nitrogen
Per cent 1.09 1.55 0.39 0.25 1.09
Per cent 1.30 1.92 0.98 0.45 1.30 1.30 2.42 1.01 0.91 1.01 1.44 1.26
0.56 2.04 0.59 1.01 1.02 1.OB 1.02
Per cent 1.44 2.03 1.54 0.77 1.93 2.39 3.02 1.40 1.96 2.03 2.42 2.24
NITROCEW
FROM AMMONIACAL SALTS
MgOOfficial
Per cent 0.14 0.11 0.56 0.32 0.63 1.09 0.60 0.39
SolutionMgO
Per cent 0.14 0.07 0.56
0.25 0.63 1.19 0.63 0.35
_
February, 1927
I N D U S T R I A L A N D ENGINEERING C H E X I S T RY
animal tankage, and cottonseed meal were added in amounts equivalent to 1, 2, and 3 per cent nitrogen, respectively. The close agreement of columns (A) and (B) by the proposed method indicates that any action of hydrogen on these materials is insufficient to offset the effect of the concentrated soda solution used. The differences found are stated in the third column, the apparent nitrate present being 0.03, 0.07, and 0.11 per cent in the samples containing cyanamide. I n four of the remaining samples the (B) column shows that the action of sulfuric acid and soda alone was even slightly greater than the iron, sulfuric acid, and soda treatment. All, however, are well within the limits of error. Against this showing compare the results obtained by the official reduced iron method, particularly in the samples containing cyanamide, where 0.56, 1.12, and 1.65 per cents
271
of nitrate nitrogen are indicated where none exists. I n the remaining samples no such variations are noted, though all show increases over those obtained by the proposed method. It seems probable that during the curing of acid phosphate, to which either cyanamide or urea has been added, these organic ammoniates may be partially converted to ammonia. This portion, if held in the mixture in the form of ammonia salts, should now be classed as mineral nitrogen, for it so exists in the material regardless of its original source. Thus far this method has been applied to laboratory mixes only, where well-cured acid phosphate was used. The writer desires that fertilizer chemists give it a thorough trial on factory mixed goods containing known amounts of nitrate nitrogen together with cyanamide and urea.
Some Economic Aspects of Texas Potash' By J. W. Turrentine BUREAU OB SOILS,WASHINGTON, D. C
T
HE establishment of unmistakable evidence of the presence of segregations of potash in the saline strata underlying a large area in western Texas and southeastern Ken- Xexico has again aroused the popular interest in American potash. It has long been the dream of those of us who have devoted our energies to the establishment of American independence with respect to this important agricultural and industrial essential that some day we should find within our own boundaries subterranean deposits of potash similar to or a t least comparable with the great German deposits. I n the days when national potash surveys were inaugurated, potash production in Germany was largely a simple mining operation, potash salts being mined and crushed and shipped to market without refining, pretty much as coal is mined and shipped in this country. A simpler or cheaper source it was hard to imagine. And i t was because of this dream of natural deposits of water-soluble potash that we were discouraged in our study of the abundant potash-bearing raw materials which we found in America, all of them requiring more or less elaborate chemical processing to render the potash merchantable. Now that we are apparently approaching the realization of our dreams, is our problem about to be solved or are we confronted by fresh disappointments? Is it not better to anticipate these than to meet them unprepared? Geological Considerations
The C . S. Geological Survey have provided many reliable data relative to the newly discovered Texas deposits. Unfortunately, these data are still largely qualitative, but even so are highly significant. I n drilling for oil in the region mentioned strata of rock salt and anhydrite have been encountered over a wide area. An examination of the balings obtained in penetrating these strata has revealed occasional high percentages of potash, first reported by J. A. Udden, of the Bureau of Economic Geology and Technology of the TJniversity of Texas, and later in more complete form by Mansfield, Hoots, and Lang, of the Geological Survey. With the churn drill there employed and with fresh water lubrication, material 'Received August 19, 1926. Presented before the Division of Industrial and Engineering Chemistry at the 72nd Meeting of the American Chemical Society Philadelphia P a , September 5 t o 11, 1926
from the strata penetrated is mixed and so affected by the solvent action of the water that it is impossible to tell whether the thickness of the potash-bearing strata is to be measured in feet or inches, or what their potash content is. However, fragments of the definite potash mineral, polyhalite (KzSO4.MgS04.2CaS04), have been obtained from Texas wells, and more recently there has been obtained a core from a continuation of the same deposit underlying southeastern New Mexico, showing, in addition to several strata of polyhalite, also sylvinite (KC1. zKaCl), kainite (KC1. MgSOa.3H20), and langbeinite (KzS04.MgSOJ. These discoveries definitely establish the presence of segregations of potash salts brought about by evaporation and crystallization processes. These segregations are found at intervals in the Permian beds and a t depths ranging from 700 to 2200 feet. The rock-salt deposits here underlie a region of an average length of 360 miles from north to south and width of 275 miles from east to west,2 embracing approximately 70,000 square miles in Texas and New Mexico. The maximum recorded thickness of the salt series is 1391 feet. Associated strata of anhydrite are encountered which increase in thickness a t the periphery of the deposits, as the thickness of the salt decreases. The borings from which potash has so far been obtained are confined, for the most part, to an area of 20,000 square miles and the potash strata penetrated are located in the upper part of the saline deposits. Under date of June 21, 1926, the Geological Survey summarizes their data in the announcement of
* * * the discovery of potash in 15 additional wells, distributed in 7 counties in the Western Texas region and in one county in New Mexico.***There are now 48 wells in 17 counties of Texas and 2 wells in 1 county in New Mexico, or a total of 50 wells in 18 counties in the two states named that have furnished potash data. * * * The laboratory examinations of the cuttings from these 15 new wells include***quantitative determination of 217 samples*** showing more than 1.5 per cent of potash (K20) while 11 yielded more than 5 per cent.***The richest sample, which contained 13.6 per cent of potash (KzO)***was taken a t a depth of 1515 feet From the geological data at hand the conclusion that these deposits are the result of the evaporation of sea water seems justified, since they appear to be comparable with or analogous to the German deposits whose marine origin is generally Hoots L; 3 Geoi Surzey Bull 780-B (December 29 1925)
