June, 1918
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
t h a t t h e precipitates must be subjected t o analysis just as if they were original substances for a n analysis. If it is found t h a t t h e composition of a precipitate comes up t o expectation fairly well, it might be sufficient t o establish a factor b y which t h e results are t o be multiplied. However, if this is not t h e case we must endeavor t o improve t h e purity of t h e precipitate. I n general, precipitates are t h e purer, t h e more dilute t h e solutions from which they have separated. Still, too great hopes i n this respect should not be entertained, for t h e ratio of t h e precipitate t o t h e substances i n solution remains t h e same on dilution, and it is t h e influence of these substances which, i n many cases, prevent t h e pure separation of t h e precipitates. T h e purpose is better accomplished if precipitation is repeated after t h e bulk of t h e first solution has been removed. Especially is this t o be recommended if t h e precipitation h a d t o t a k e place in highly concent r a t e d solution. If removal of t h e impurities is impossible, nothing else remains t o be done b u t t o make determinations with varying quantities in order t o arrive a t an estimation of t h e a m o u n t of impurities, taking into account any losses caused b y t h e solubility of t h e precipitate. If a t t h e same time t h e possibility of incorrect stoichiometric composition prevails, such results, of course, allow more t h a n one explanation. F r o m t h e aforesaid it is clear t h a n two radically different methods of procedure are necessary t o criticize precipitation methods. T h e completeness of precipitation a n d t h e losses on account of solubility must be studied on small quantities. As a matter of f a c t , a few milligrams of t h e substance are sufficient in most cases, Simultaneously we learn from this p a r t of t h e critical work on a method t h e limit of its applicability for t h e determination of small quantities. I n order t o characterize these conditions I would like t o introduce t h e t e r m “micro-analytical.” On t h e other hand, examinations as t o purity a n d correct composition, likewise t h e final tests with t h e view t o practical application, must be made with large quantities. For these reasons I would like t o call this p a r t of t h e criticism of t h e method “macro-analytical.” For another reason also i t would be well t o make such distinction. T h e micro-analytical errors are always absolute losses. Accordingly their corrections will consist i n additions. But t h e macro-analytical errors have t h e form of p r o p o r t i o m and must, therefore, find their corrections i n multiplications or divisions. T h e general algebraic formula for t h e correction of a result will be t h u s :
Q X M 1 X h/12
+ m1 + m2
in which Q represents t h e actual quantity of a precipitate, M1 a n d M2 t h e factors for t h e macro-analytical corrections a n d *a1 a n d m2 t h e losses caused by solubility. While methods requiring corrections have not been considered t h e best, there is no reason why one should hesitate t o use a method after i t h a s undergone a thorough critical t r e a t m e n t ; in other words, after t h e errors have been scientifically determined. On t h e
429
contrary, results corrected on a scientific basis deserve more confidence t h a n such as are obtained by methods which are believed t o be reliable, b u t which never have been criticized in a methodical manner. 25 OGDENSTREET HAMMOND, INDIANA
IMPROVED METHODS FOR THE ESTIMATION OF SODIUM AND POTASSIUM B y S. N. RHUE Received September 19, 1917
A method for t h e estimation of sodium, involving considerable modification of t h e procedure of t h e Association of Official Agricultural Chemists, was published from this department b y Forbes, Beegle and Mensching in Bulletilz 255 of this Institution, under t h e date of January 1913. Since t h e time of this publication we have made extensive use of this improved method and have devised further improvements, which i t is our purpose t o record. T h e general principles of t h e method as now used are t h e same a s stated in the earlier publication referred t o above, b u t changes of detail have been devised which shorten t h e process and remove certain sources of possible error, a t t h e same time calling for much less use of platinum. Incidentally, improvement has been effected in t h e method for t h e estimation of potassium. For t h e quantitative test of t h e new procedures a salt solution was prepared i n such manner as t o contain t h e same kinds and proportionate amounts of t h e mineral elements as are present in wheat b r a n . Nitrogen, also, was added t o this solution, in t h e form of ammonium sulfate. T h e elements and t h e cornpounds in which they were present were as follows:
............................. ............................. ............................... ............................ ............................... .............................. .......................... ..............................
Sodium.. Potassium Calcium Magnesium Sulfur.. Chlorine Phosphorus.. Nitrogen
CzI-IiONa CzHsOK CaHPOdHzO Mgs(POr)t.4HzO HzSOa and (NH4)zSOd HC1 Salts of Ca and Mg
(NHn)zSO4
T h e sodium and potassium ethylates were prepared from t h e pure metals by dissolving in absolute alcohol and standardizing by titration against benzoic acid. Calculated from t h e weights of t h e metals (in air), I O cc. of t h e solution should have conta’ined 0.0104j g. Na and 0.03926 g. K. T h e titration against benzoic acid indicated t h e presence of 0.0103 7 g. N a and 0.037j7 g. K (0.03202 g. sodium sulfate and 0.08373 g. potassium sulfate) in t h e same volume of solution. T h e latter weights were used as t h e basis for judgment as t o t h e correctness of analytical methods. MODIFICATION
OF THE
METHOD
FOR
SODIUM
I n t h e use of t h e method for sodium, as published i n Ohio Agricultural Experiment Station, Bu1leti.n 2 5 5 , we have found much advantage i n t h e principle of t h e second of t h e optional methods of ashing. T h e first method proposed for destroying t h e organic matter, b y nitric-sulfuric acid digestion, necessitates t h e subsequent burning off of much sulfuric acid, i n which process there is great likelihood of loss through spattering and overheating. In our later work,
,
430
T H E JOUR,VAL O F I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRE'
therefore, t h e principle of t h e second optional method of ashing (in which t h e little sulfuric acid used is entirely driven off) has been followed, a n d t h e ashing is now conducted in porcelain, instead of platinum. After t h e precipitation of t h e phosphorus, in t h e solution of t h e ash, as magnesium ammonium phosphate, t h e published method specified t h e evaporation of t h e filtrate a n d t h e burning off of ammonium salts i n a platinum dish. In t h e later work, t h e a m monium salts are destroyed b y digestion with nitric a n d hydrochloric acids, these acids being finally driven off, first b y evaporation and t h e n b y baking on t h e hot plate. T h e details of our later method for t h e estimation of sodium are as follows: Weigh the sample into a porcelain dish, cover with 25 per cent sulfuric acid, reduce to dryness on the steam bath, and char completely on the hot p1ate.l After all foaming has ceased, ash over an open flame. If necessary, to complete the ashing, leach with hot water, and reburn the residue. Digest the ash and leachings in HC1 and water on the steam bath for one hour, and filter into a 400 cc. beaker, washing the residue on the filter paper with hot water; or, in case the same solution is to be used for both sodium and potassium estimations, filter into a volumetric flask. Add enough ammonia to the solution to render it almost neutral,2 and enough magnesia mixture to precipitate the phosphorus as magnesium ammonium phosphate. After 15 minutes add 5 to I O cc. of concentrated ammonia, and allow to stand over night. Filter, and wash out sodium and potassium sulfates with 2 . j per cent ammonia. Now add 20 cc. of concentrated " 0 % and a little HC1, and evaporate to dryness on the hot plate. Continue heating for I or z hrs. to drive off all excess acid. Dissolve the residue of sulfates with hot water and transfer to a 250 cc. beaker. Boil, and add a saturated solution of freshly prepared Ba(OH), to the complete precipitation of the magnesium. Filter, and wash with hot water, testing the filtrate for complete precipitation of magnesium. (If the filtrate is milky it is an indication of incomplete precipitation of magnesium.) After all the magnesium is filtered out make the solution ammoniacal, boil, and add enough ammonium carbonate and ammonium oxalate (saturated solutions) to completely precipitate the barium and calcium. Allow to stand at least 2 hrs.; filter, wash with hot water, add j cc. ammonium sulfate solution (75 g. ("4)$S04 per liter) and evaporate to dryness. Dissolve the residue in hot water and transfer directly to unweighed platinum dishes. Evaporate t o dryness on the steam bath and heat carefully over a free flame to dull redness. Dissolve residue in hot water and filter into weighed platinum dishes. Evaporate to dryness on the steam bath and heat t o constant weight over the open flame. The residue weighed consists of the sodium and potassium sulfates. Calculate the amount of potassium found to the sulfate, and subtract from the weight of combined sulfates t o obtain the amount of sodium sulfate. MODIFICATIOX OF T H E METHOD FOR POTASSIUM
Potassium was estimated by t h e official Lindo1 The burning of the sample in a porcelain dish with H2S04 does not introduce an error by removing potassium or sodium compounds from the To determine this point 10 g of chemically pure sugar and 25 cc. dish of 25 per cent H2SO4 were burned in new and in old porcelain dishes, and potassium and sodium were determined by these methods. 2 Recent unpublished work in this laboratory by J. 0. Halverson has shown t h a t manganese and aluminum, if present, should be precipitated and removed a t this point.-(&. B. Forbes)
Vol.
IO,
No. 6
Gladding procedure, modified as t o t h e method of ashing, and also for preliminary precipitation of calcium a n d iron, where such treatment is necessary. T h e details of t h e method as used are as follows: Prepare and digest the ash in the same manner as specified for sodium above. Make the solution ammoniacal; boil and filter, washing well with hot water. Heat the ammoniacal filtrate to boiling and add sufficient ammonium oxalate (saturated solution) to completely precipitate the calcium. Allow to stand over night. Filter, and wash with z ..=per j cent ammonia. Add 20 cc. of concentrated HNOa and a little HCI; evaporate t o dryness and bake on the hot plate for I or 2 hrs. to drive off excess nitric acid. Take up the residue with hot water and a few drops of HC1; filter into a I j o cc. beaker. Add enough HzPtCle solution for the complete precipitation of potassium. Evaporate the solution on the steam bath almost to dryness, cool and add a few cc. of 80 per cent alcohol. Filter through a small sugar tube, and transfer the precipitate to the tube by means of a rubber-tipped rod and 80 per cent alcohol. Wash the precipitate and asbestos free from HzPtCle with 80 per cent alcohol. Wash the precipitate about five times with 5 to I O cc. of NH4Cl solution (100g. NH&l in 500 cc. HzO saturated with KzPtCle) or until all white or light orange material is dissolved. Then wash the precipitate and pad free from NHC1 with 80 per cent alcohol and drive off the alcohol in a hot-air oven. Wash the KzPtCle, with hot water, from the sugar tube into a weighed platinum dish; evaporate to dryness on the steam bath, and heat to constant weight in a hot-air oven at 105' C., weighing as KzPtC16. ANALYTICAL RESULTS OBTAINED BY MODIFIED METHODS
Estimation of sodium in the test solution, b y t h e improved method, gave results as stated below: Combined sulfates found in 10 cc. solution.,
...........
AVERAGE......................................
...........................
ACTUALLY PRESENT..
Gram 0.1131 0.1135 0.1139 0.1141 0.1143 0.1153 0.1169 0.1173 0.1148 0.11575
This method was found much superior t o t h e usual procedure, b o t h as t o ease of operation and agreement of results. The a m o u n t of sodium found was g g per cent of t h e a m o u n t present. SODIUMESTIMATIONS O N FOODSTUFFS-DRY BASIS Combined Potassium Sodium Com- sulfates sulfates sulfates SAMWt. of bined per gram per gram per gram sample sulfates sample sample sample Per cent PLE No. FOODSTUFF Grams Gram Gram Gram Gram sodiuIp 1 Corn meal 10 0.0838 ... ... ... 2 Corn meal ... 10 0.0870 ... ... ... .. 3 Corn-meal ... 10 0.0850 AVERAGE. 0.0853 0.06853 0.00j70 0.00083 0.2269 1 Corn silage.. 5 0.0824 ... ... ... .. 2 Corn silage.. 5 0.0820 ... ... ... 3 Corn silage.. 5 0 0808 AVERAGE. . . 0:08ii 0.0i634 0.61463 o . 0 0 i i i 0.0S54 oil 1 Linseed ... ... .. meal . . . . . . 3 0,0832 ... 2 Linseed oil meal . . . . . . 3 0.0822 ... ... ... .. 3 Linseed oil meal . . . . . . 3 0.0818 AVERAGE. , . 0.0824 o . O i j 4 i o.oik1i 0.06130 0 . 0 4 2 ~ 1 Wheat bran. 3 0.0860 , . ... .. 2 Wheat bran. 3 0.0846 ... ... ... .. 3 Wheat bran. 3 0.0808 AVERAGE. 0.0838 o . o i j 9 3 o . , o i i 9 i 0.00002 0.6007 3 0.1834 ... ... ... .. 1 Alfalfa.. . . . . 3 0.1860 ... ... .. 2 Alfalfa.. . . . . 3 0,1860 3 Alfalfa ...... AWRAGE 0.1851 o.oki7o 0.65549 o.Ook21 0.i01 I
..
...
..
..
.
...
..
.
. . .
.
I
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 CHEMISTRY
June, 1918
Estimation of potassium in t h e test solution, b y t h e improved method, gave results as stated below:
.
Potassium (as platinic chloride) found in 10 cc. solution.
Gram 0.2247 0.2247 0.2269 0.2275 0.2285 0.2291 0.2299 0.2305 0.2311
-
AVERAGE .......................................
0.2281
ACTUALLY PRESENT.. ............................
0.2336
Results obtained b y t h e usual method were high, a n d t h e agreement was not satisfactory, probably because of incomplete washing o u t of t h e calcium a n d magnesium sulfates with ammonium chloride solution. T h e improved method of ashing converts t h e calcium a n d magnesium into t h e chlorides which are easily washed o u t with ammonium chloride solution. T h e agreement of results by t h e improved method is satisfactory, a n d t h e amount of potassium found was 98 per cent of t h e a m o u n t present.
43 1
did n o t give results t h a t were peculiar t o their ultimate composition a n d chemical structure. I t was hoped in this way t o throw further light on t h e chemical structure of t h e substances in coal, b y comparing the results obtained from organic compounds with those obtained from coal when treated in t h e same way. T h e experiments were carried o u t in a vertical, electrically heated, iron t u b e furnace, 4 in. in diameter a n d a little more t h a n 6 ft. long. T h e substances examined were powdered coal, gasoline, kerosene, gas oil, benzene a n d naphthalene. T h e coal used was a Pennsylvania gas coal of t h e following composition: Proximate, per cent.. Ultimate, per cent..
Moisture Volatile M a t t e r Fixed Carbon Ash 0.9 34.1 59.2 5.8 Carbon Hydrogen Nitrogen 80.2 5.7 1.6
.........
..........
I n t h e experiments in which powdered coal was used, it was fed in b y a worm conveyor from a hopper a t the
POTASSIUM ESTIMATIONS O N FOODSTUFFS-AIR-DRYBASIS Potassium platinic Potassium Potassium chloride sulfate . .Wt. of platinic per gram per gram SAMPLE sample chloride sample sample Per cent No. FOODSTUFF Grams Gram Gram Gram potassium 1 Corn meal . . . . . . . . . . . 5 0.1083 ... ... .. 0.1163 ... ... 2 Corn meal . . . . . . . . . . . 5 .. 3 Corn meal.. 5 0.1065 AVERAGE1 and 3 . . ... 0.1074 O.Oii48 O.OOj70 0.3455
.........
1 2 3 1 2 3
Corn silage.. . . . . . . . . Corn silage.. . . . . . . . . Corn silage .......... 2 AVERAGE..
........... Linseed oil meal.. .... 1.5 Linseed oil meal ...... 1 . 5 Linseed oil meal ...... 1.5 AVERAGE.. ........... Wheat b r a n . . ....... 1.5
1 2 Wheat bran. . . . . . . . . 3 Wheat bran.. . . . . . . . AVERAGE 1 and 3 . .
1 2 3
1.5 1.5
... .............. 1 . . . . . . .~.. . . . 1 .............. 1 ...........
Alfalfa Alfalfa. Alfalfa AVERAGE..
0.0937 0.0913 0.0897 0.0916 0.1083 0.1115 0 1087 0 : 1095
... ... o.OiOso
... ...
o.Oijoo
... ...
0.i i k o
..
0.Oii63
0.262
... ...
.. ..
o.Oi617
1. i j 4 i
0.1147 Dish broke dukng ignit'ion 0.1189 0.1168 0.0+?86 O.Oii9l 0.1561 0.1539 0.1545 0.1548
..
... ...
... .
I
.. 1.2523
.. ..
.
o.Oi549
2.4898
DEPARTMENT OF NUTRITION EXPERIMENT STATION OHIO AGRICULTURAL WOOSTER,OHIO
A COMPARATIVE STUDY OF THE THERMAL DECOMPOSITION OF COAL AND OF SOME OF THE PRODUCTS OF ITS CARBONIZATION1 By M.
c.
WIlrTAKER AND JOHN RICHARDSUYDAM, JR.
T h e work of Whitaker a n d R i t t m a n , 2 E g l ~ f fAlexan,~ 'der,4 Leslie,6 Zanetti,6 a n d others has shown t h a t it is possible t o control t h e thermal decomposition of hydrocarbons in such a way as t o give t h e maximum yields of certain products of decomposition, such as constituents of gases, aromatic hydrocarbons, etc. The purpose of this investigation was t o determine i f different hydrocarbons a n d other organic compounds 1 Abstract of dissertation submitted in partial fulfillment of the requirements for the Ph.D. degree, Columbia University, New York City, 1917. * THISJOURNAL, 6 (19141, 383, 472. 8 Met. and Chem. Eng., 7 (1915), 16, 17; J. Phys. Chem., 1916; THIS JOURNAL, I (1915), 481, 578, 1019. THISJOURNAL, 7 (1915), 484. 6 I b i d . , 8 (1916). 593. 684. 0 I b i d . . 8 (1916); 674, 777.
t o p of t h e furnace. T h e powder dropped through the heated furnace, some of i t sticking t o the walls, and the coke was collected below. T h e gas formed was led off f r o m t h e bottom of t h e furnace t o a gasometer. Experiments were carried o u t studying the effect of temperature, rate of feed, a n d size of coal particles on the production a n d composition of the gas. T h e results are summarized i n the table on page 432. T h e q u a n t i t y of t a r produced was too small for examination. I n the work on the thermal decomposition of the other substances examined, the liquid was fed into the
