Dec., I 9 I 6
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
SOME COMPARISONS OF METHODS FOR DETERMINING NITROGEN IN SOILS By W. I,. LATSHAW Received August 14, 1916
Since determinations of nitrogen in soils have been made b y t h e Kjeldahl method or some of its various modifications, considerable trouble has been experienced with t h e flasks bumping while distilling t h e ammonia from t h e digest. I n some cases t h e bumping is so violent t h a t flasks are thrown off t h e still. This is very annoying, especially when using glass flasks. Various means have been proposed t o meet the trouble as: ( I ) Distilling with steam; ( a ) Transferring digest t o a copper flask and allowing it t o bump, t h e danger of t h e flask breaking being eliminated. These methods answer t h e purpose, b u t ignore t h e real issue-the cause of t h e bumping. Furthermore, they are both laborious and consume considerably more time t h a n would a satisfactory method b y which t h e distillation could be made in t h e same flasks as t h e digestion. T o perfect a method of this nature, we had t o know t h e cause of t h e bumping. I n our regular work in which we diluted our digest t o 600 cc. before distilling. using 800 cc. flasks a n d t h e same amount of zinc as when we diluted t o loo cc. before distilling, we noticed t h a t very little bumping took place, while those diluted t o t h e less extent bumped considerably. Thus it would seem t o be a problem of diluting t h e heavy alkaline digest1 which consists of sand and a heavy voluminous precipitate of the metals in the soil which are precipitated by sodium hydroxide. TTe also decided t h a t if the heal-y metals in the soil were causing t h e trouble, t o add more in t h e form of mercury and mercuric oxide would cause more trouble, so t h e Gunning method was tried and comparison made with t h e Kjeldahl method using mercury, the same dilutions being made in each method. It was found t h a t where no mercury was used, there was no bumping. T h e Gunning method proved in every way satisfactory in respect t o eliminating t h e bumping, b u t required considerable time for digestion, in some cases as much as 4 or j hours. As this length of time was objectionable, a catalyzer was thought necessary and copper wire was used in 0.08 t o 0.1 g. amounts with excellent results. The time of digestion was reduced t o a n average of 2 ‘ 1 2 hrs. for each determination. XETHOD U S E D AT T H I S S T A T I O K
Place I O g. of soil in a n 800 cc.2 Kjeldahl flask with 7 g. of powdered sodium sulfate, approximately 0.08 t o 0 . I g. of copper wire and 3 5 cc. of pure concentrated sulfuric acid. Shake immediately t o prevent t h e soil from adhering t o the sides of t h e flask. Heat over a moderate flame, rotating or shaking occasionally so as t o secure even and complete digestion. Continue t h e digestion one hour after t h e solution becomes colorless. Cool and dilute with j o o cc. or more of water. Add a n excess of strong alkali and a small amount of 1 The principle of diluting the digest has been in use in this laboratory for the last five or six years and the author rlaims no credit for this idea. 2 Pyrex flasks were used exclusively in doing this work. We have found them superior to the well-known Jena flasks.
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zinc dust or granulated zinc, preferably t h e latter. Connect t h e flask with t h e distilling apparatus, mix thoroughly a n d distil, etc. I n order t o demonstrate more clearly the chemical efficiency of t h e method used a t this Station, t h e results of some experimental work are given in comparison with t h e Official Meth0d.l The results, given in Table I, show no marked differences in the two methods. TABLE I-COMPARISONOF PERCENTAGES NITROGEN BY
Sample 1383 1384 1385 1386 1387 1388 1389 1390 1091 1392 1393 1394
METHODUSED A T THISSTATION No. of Det’ns Max. Min. Av. 4 0.151 0 . 1 3 6 0.143 2 0.147 0.144 0.146 2 0.147 0.144 0.146 2 0.155 0 . 1 5 4 0.155 2 0.140 0.137 0.139 3 0.146 0.137 0.141 3 0.147 0.142 0.144 3 0.151 0.145 0.148 2 0.146 0.144 0.145 2 0.156 0 . 1 5 4 0.155 2 0.146 0.144, 0.145 2 0.147 0.146 0.147
TWO
METHODS
OFFICIAL METHOD No. of Det’ns Max. Min. Av. 3 0.145 0.142 0 , 1 4 4 3 0.147 0.145 0.146 2 0.148 0.146 0,147 2 0.160 0.158 0.159 2 0.143 0.139 0.141 2 0.143 0.140 0 . 1 4 2 ’ 2 0.142 0.140 0.141 2 0.146 0.143 0.145 2 0.144 0.143 0 , 1 4 4 2 0.153 0.153 0.153 2 0.142 0.140 0.141 2 0.146 0.145 0.146
As a means of showing t h e working efficiency of our method, some work may be described which was recently done with t h e aid of two student helpers, each working half time. We had 475 samples of soil t o analyze for nitrogen which, including duplicates and t h e blanks on several lots of alkali and several repeats, made approximately 1000 determinations. We used. one hundred and twenty 8 0 0 cc. Kjeldahl flasks and a I a-place block-tin condenser. Our average run was I O O determinations a day. Only two flasks broke, both of which fused dry in digestion. One of these broke after the distillation was completed. The other represents our sum total of losses in determinations due t o breaking of flasks. CHEMICAL LABORATORY, KAN5AS STATE AGRICULTURAL COLLEGE MANHATTAN, KAXSAS
THE DETERMINATION OF PHOSPHORUS PENTOXIDE AFTER CITRATE DIGESTION By 0 . C. SMITH Received June 27, 1916
Considerable difficulty is experienced b y most chemists in t h e digestion of t h e fertilizer and filter papers left after t h e removal of t h e reverted phosphate by t h e digestion with neutral ammonium citrate. The usual ‘method consists in the digestion with differing proportions of hydrochloric and nitric acids, preferably 30 cc. concentrated nitric and I O cc. concentrated hydrochloric. By this method a clear solution cannot be obtained with some fertilizers even after digestion for a whole day. By t h e use of t h e following method a clear solution can be obtained in less t h a n a n hour. Two grams of t h e sample are weighed on a filter paper in a funnel a n d washed with about Zjo cc. of water: t h e paper a n d sample are then transferred to a zoo cc. flask containing I O O cc. of neutral ammonium citrate, previously heated t o 60’ C. and heated a t 60’ with frequent shakings for l/z hr. The contents of t h e flask are then filtered immediately and washed with water a t 6 0 ” until all of t h e citrate solution and soluble phosphorus are removed. The two filter 1
“Soil, Total Nitrogen, Official,” .4. 0. A . C., No. 4, 1 (1916). IO.
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T H E J O U R A T A L O F I N D U S T R I A L A N D ENGINEERI?;G C H E M I S T R Y
papers and remaining fertilizer are t h e n ready t o be dissolved. T h e contents of the funnel, including both filter papers, are p u t back into t h e Erlenmeyer flask, I O cc. concentrated sulfuric and j o cc. of dilute nitric acid ( I : I ) are now added and t h e flask placed on t h e bare hot plate. T h e digestion is allowed t o proceed undisturbed until all of t h e nitric acid has been boiled off which is shown b y t h e appearance of t h e white sulfuric acid fumes. About I or z cc. of concentrated nitric acid i s now added t o t h e boiling sulfuric acid and t h e digestion continued until v-hite fumes appear again. Concentrated nitric acid is then added again and t h e digestion continued. This is repeated till the solution is water-white, then i t is allowed t o cool, made up t o volume and a n aliquot taken. This is neutralized rritEl ammonium hydroxide, ammonium nitrate added and t h e phosphorus precipitated in the usual way. By using this method of digestion a clear solution is easily obtained in a n hour or less. T h e second addition of t h e nitric acld will almost always clear it up. H o w e l w . if the sample is heated after t h e sulfuric acid is added a n d t h e n the dilute nitric acid added considerable difficulty with foaming will be experienced. OK1 A I I O V 4
AAGRICULTURAL EXPERIMENT S T A T I O h
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Yol. 8 , SO.1 2
in France as “gelose,” i t is synonymous with Bengal or vegetable isinglass. T h e Ceylon and Chinese agars are derived mainly from Gracillaria coTzjzSerooides and give with water a clear, transparent jelly. The product obtained from J a v a and Malaysia conies principally from Eucherna spiiiosztm and is of inferior quality. The Japanese agar, obtained from G d i d i u m corncum, is ordinarily accounted t o be of superior quality t o other agars. hlr. Y. S. Djang, of Tientsin, Southern China, has informed t h e author t h a t t h e Japanese product is also considered best in China from a dietary standpoint. “Carragheen” or Irish moss should not be confused with agar. I t is derived from Clzrondus crispus mainly, an alga which is very abundant in t h e North Sea. I t gives a gel resembling agar Agar is prepared for market in two ways: One method consists merely in Trying and bleaching t h e thallus of t h e algae i n , t h e sun, previous t o shipping. Such a product contains many impurities like diatomaceous refuse and other mineral or vegetable matter foreign t o t h e plant T h e other method consists in making a jelly of t h e seaweeds, allowing t h e water t o freeze out, and finally cutting t h e residue into thin strips and drying thoroughly. T h e commercial product usually consists of a number of different species of algae and hence its composition i s fairly constant.
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THE ANALYSIS, PURIFICATION AND SOME CHEMICAL PROPERTIES OF AGAR AGAR By CARL R. FELLERS Received M a p 8, 1916 S O U R C E S O F AGAR
Agar is t h e commercial name applied t o t h e dried a n d more or less purified stems of certain kinds of marine algae. Of these t h e group Florideae or red algae is b y far the most common, They are char-
A N A L Y S I S O F AGAR C O X P I L E D F R O M V A R I O U S S O U R C E S
T h e folloming analyses are thirty t o forty years old except t h e one by Forbes, Beagle and Mensching‘ which is more recent and which gives a fairly complete analysis of a sample of dried agar. These results show how widely the composition of agar varies from different sources or even from t h e same source. The high - ash content shown by Analysis 2 , points t o gross mineral impurities, while the low
TABLEI-ANALYSES OF ALGAEPRODUCING AGAR Euchema & Unknown Euchema Gelidium Gelidiuin corneum Dried Dried Dried SPECIES 4 5 2 Analysis h-0.. . . . . . . . . . . . . . . . . . . . 1 3 18.5%; 49.80 17.33 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8% 19.56 2.88 3.62 9.8 h’itrorenous M a t t e r . . . . . . . . . . . . . . . . 1 1 . 7 1 2.53 0.24 0.20 .... F a t . .T. . . . . . . . . . ..... 12.02 3.15 18,96 2.89 Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.44 Dried -. ........Plant 5.00 3.20 0.47 Woody Fiber.. . . . . . . . . . . . . . . . . . . . . . . . . ..... Carbohydrates.. . . . . . . . . . . . . , . , . . . . . 65.05 .... ..... .......... 52.00 N-free E x t r a c t . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . . Fat DRIED PLANT 12.02 .......... Nitrogenous M a t t e r . . . . . . . . . . . . . . . . . 14.06 3.15 !. 9 2 .......... 2.35 0.50 Nitrogen.. . . . . . . . . . . . . . . . . . . . . . . . . . .(.‘ N-free Extract $. Crude Fiber.. . . . . . . . . . . 73.6 .... .......... Fat Crude Fiber -t. N-free Extract.. 62. 05 .... 19.16 45.00 ..... N-free E x t r a c t . . ........................ i88p About 1885 Date of Analysis.. . . . . . . . . . . . . . . . . . . 1884 1883 ......................... Kellner(o) A‘agai & Iionig(a) Sack and Van Eck ANALYST.. Murai(a) and Greshoff ( a ) J. Konig, Chemie der Menschlichen n’ahru ngs und Ge nztssmiltel, Band I, S. 721.
+
+
acterized by a leaf-like growth and upright thallus and grow almost exclusively in tropical waters. T h e most important of these are Gelidizim c o r n e w n , G. c a r t i l a g i n e m z , F u c u s my lace us (also called Gracillarin coizjervoidesj, and E u c h e r n a s p i n o s z t m A g . , h u t agar may also be obtained from cert.ain species of Telzar a n d Gigartineae. Most of t h e agar of commerce comes from China, Japan, Malaysia, Ceylon and neighboring coasts. I n C h i m i t goer b y t h e name Rai-Thao or Ta-o,
DRIED AGAR
Fuczis Amylaceus
6
I
Water Albuminoids Solution in Cold Water Ash 0.89 Solution in Dilute N a O H 1.77 Gelose (Metarahin) Ca, 0.66 M g , 0.483 Solution in Alcohol 0.114 Wood gum h-a, K, 0.112 Cellulose C1, 0.034 P, 0 020 M a t t e r removed by KKO3 77.34 1882 1913 3reenish Forbes, Beagle & Mensching 15:29 ! .88 0.37 4.23
s,
+
Loss
15.07 7.48 2.7 10.24 6.52 36.71 0 10 4.17 10.17 3.40
ash and high carbohydrate percentages in Analysis j s h o v careful purification. Euchema is seen t o be inferior t o Gelidium as a source of agar. Analysis 7 gii-es some interesting information as regards t h e crganic composition of agar. Forbes’ results show a very high perce2tag.e of sulfur. Frankland2 reports t h a t he found one liter of agar jelly t o contain 0 . 3 0 ~ 6g. sulfur. Arsenic is reported t o be present by Leroide 1 2
Ohio Agr. Exp. Sta., Bd1. 265. “Microijrganisms in Water,“ pa 14.
