A%., 1917
T H E J O C- R N A L 0 F I-V D 1‘s T R I A L -4 D E 4 G I 1VE E R I i i G C H E M I S T R E’
n o offerings. Under normal conditions liquid storax will average about $ 0 . 2 0 per lb., b u t even then i t is t h e worst adulterated material ever examined in our laboratory, being adulterated with Burgundy pitch, colophony, castor oil a n d extracted storax. At $ 0 . 2 0 per pound American storax cannot compete, unless some cheap method of production can be worked o u t ; t h e Forest Service is now busy on this problem. I t is believed, however, t h a t this material can be obtained for $ 0 . j o t o $1.00 per pound and t h a t after a market is found t h e supply may warrant a material reduction.
77=
coKcLcsIos
I t would seem t h a t “sweet gum” may be used in t h e place of liquid storax with good results; t h a t it carries more cinnamic acid t h a n commercial storax; t h a t t h e odor and fixative properties of “sweet gum” are superior t o t h e commercial variety of storax imported into t h e United States; t h a t t h e southern portion of t h e United States should furnish all t h e storax required; t h a t t h e old hardened balsam may be used in t h e manufacture of chewing gum. CHEMICAL DEPARTMENT, AMERICANTOBACCO COMPANY 60 F R l N K L I N A V E K U E , BROOKLYN, S . Y.
LABORATORY AND PLANT NITRIC ACID SOPHISTICATION, A SERIOUS PRODUCTION MENACE’ Commercial nitric acid is shown in this paper t o be capable of sophistication by sodium nitrate or other sodium salts-an adulteration which may have a serious effect on production, or upon yields in many chemical operations, and which may easily escape detection when t h e strength of acid is ascertained b y determining specific gravity, or, in t h e case of sodium nitrate, b y determining 5 0 3 content as well. I t follows t h a t other comrnercial acids may be subject t o similar possibilities. Dissatisfaction with t h e nitric acid return from t h e recovery system in a chemical plant in Ohio led t o investigation of various factors entering into t h e situation. About t h a t time t h e operating chemical engineer called attention t o t h e fact, which he h a d just discovered, t h a t t h e workmen h a d been frequently noticing a small amount of a white material rattling out of t h e carboys when t h e y were up-ended t o pour out t h e last of this nitric acid. T h e discovery was made in a shipment of “Aqua Fortis 40’ Pale.” h “handful” of t h e crystals saved for inspection looked suspiciously like poorly developed rhombohedrons of sodium nitrate, though i t was felt t h a t t h e y surely must be sodium sulfate or acid sulfate from a “boil-over” during nitric acid manufacture. A qualitative examination revealed only a trace of sulfates while t h e nitrate test was strong even after much washing. Subsequent partial analysis showed SO3 1.0; per cent a n d N a 37.39 per cent. I t seemed probable, therefore, t h a t this particular shipment of acid, a t least, was saturated with sodium nitrate. P a r t of our unduly high nitric consumption a n d poor recovery could be caused b y this fact if sodium nitrate were soluble t o a n y extent in t h e acid. This seemed improbable when one remembers how easily concentrated acids precipitate soluble salts upon addition t o t h e aqueous solutions of many such salts. The specific gravity alone h a d been utilized in checking shipments of acid as they arrived a n d it is evident t h a t t h e nitrometer also would be likely t o give unreliable results in such a case. Titration would, of course, detect adulteration with any salt b u t is
little used because of t h e common presence of free sulfuric acid. We a t once resorted t o evaporation for residual salt determination a n d proceeded t o investigate carefully t h e whole matter t o see if our operation economy difficulties were chargeable t o any extent t o this sodium nitrate content in t h e nitric acid. It was obvious t h a t if sodium nitrate were soluble t o any extent in nitric acid i t would be profitable t o get t h e desired specific gravity or even NO3 content in nitric acid manufacture b y adding sodium nitrate, thus saving t h e expense of sulfuric acid, yield troubles, upkeep and depreciation. At 9 cents per pound a t point of shipment, t h e selling price of t h e acid in question, t h e returns on t h e investment should be reasonable. I n fact, as a n k d -+rial ~ chemical achievement other discoveries and developments in nitric acid production ir. recent years would be puny in manipulation saving, alongside of this method of “butting up” nitric acid, and also as far as t h e ledger is concerned. The solubility of sodium nitrate in nitric acid of various strengths could not be located in t h e literature for t h e acid concentration we were using, though i t does exist for weaker acids.’ This work gives d a t a which show t h a t 34 per cent “ 0 3 (2j.j’ Be.) will dissolve 7 per cent NaT\T03 which raises t h e mixture t o about 30’ Be. I t seemed likely t h a t if sophistication had been practiced either solid sodium nitrate was dissolved in weak nitric acid, or in strong nitric acid which was then diluted t o 40’ BC., after t h e whole had been warmed in each case and allowed t o cool in contact with excess sodium nitrate t o avoid supersaturation; or, a saturated solution of sodium nitrate was added t o weak nitric acid a n d t h e excess (precipitated) sodium nitrate, if any, used in preparing t h e next batch of sodium nitrate solution; or, strong nitric acid was added t o saturated or strong sodium nitrate solution a n d t h e mixture diluted t o 40’ BC. T o such fortified solutions water or sodium nitrate solution could be added t o reduce t h e specific gravity t o t h e required strength if t h e nitrate addition had raised it. The use of solid nitrate would require heating of t h e mixture-a manufacturing difficulty. Our interest was t o right t h e troubles arising as a result of this bad nitric acid and this was accomplished
Read before the American Institute of Chemical Engineers, Cleveland Meeting, June, 1917
1 Engel, Compf v e n d , 1887, 911, A Seidell, “Solubilities of Inorganic and Organic Substances ” Van Nostrand, 1907, p 307.
By
JAMES
R. WITHROW
,
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
772
in p a r t by changing t h e source of acid. KO exhaustive laboratory investigation was conducted b u t merely sufficient work t o insure our position in case of controversy, for i t was stoutly maintained b y acid-makers t h a t no material amounts of N a N 0 3 or other salts could be held i n solution. Though many d a t a were accumulated, details need not be given, as they were necessarily complex a n d t h e end results sufficiently emphasize t h e facts. THE
POSSIBILITIES USING SOLID SODIUM XITRATE
Nitric acid of various strengths was found t o dissolve considerable sodium nitrate a n d this was facilit a t e d b y heating t h e mixture. Table I shows d a t a obtained when a nitric acid (42' Be.) was diluted with water t o various strengths a n d t h e specific gravity taken, and these solutions t h e n warmed t o slight fumes with solid sodium nitrate a n d allowed t o cool t o t h e indicated temperature in contact with excess nitrate crystals in each case. TABLE I Sp. Gr. 1.381 1.381 1.343 1.324 1.037
Gravity Be. 40 40 37 35.5
....
NITRICACID Per cent NaNOa Dissolved on Basis of Acid Taken 3.24 3.96 4.70 5.74 70.94
.-FINAL Sp. Gr. 1.401 1.392 1.368 1.356 1.366
SOLUTIONGravity BC. 41.5 40.8 39.0 38.0 38.9
Tpp. C. 15: 22 15' 15' 15'
It follows from t h e general trend of Curve I, which gives t h e specific gravity of acid which will dissolve t h e amounts of N a N 0 3 indicated, t h a t as t h e specific
gravity of t h e curve falls off t h e solubility of sodium nitrate in t h e nitric acid rapidly increases. Curve I1 shows t h e displacement or increase in specific gravity b y solution of N a N 0 3 in t h e acids of different specific gravities, showing t h e great displacement a t low acid concentrations. T o see how much water could be added t o a saturated solution of sodium nitrate in nitric acid which was originally 40' BC. without lowering t h e final gravity below 40' BC., some 42' BC. acid (sp. gr. = 1.408) was diluted t o sp. gr. 1.381 (40' Be.), requiring about 9 per cent water. Excess sodium nitrate was then added a n d in 30 minutes t h e sp. gr. was 1.40 (41.4' Be.). Water was then added until sp. gr. had returned t o 1.381 (40' Be.). T h e temperature rose slightly during t h e operation. T h e nitrate dissolved at 15' C. was 3.24 per cent of t h e weight of t h e 40' BC. acid used. This permitted 6.0 per cent water t o be added without lowering t h e gravity below 40' BC., or 9.24 per cent total addition b y weight. Curve I11 shows t h e rise in density a n d gain in weight due
Vol. 9, No. 8
t o t h e solution of NaNO3 in 40' BC. acid and t h e fall i n density a n d total gain in weight upon adding water. When saturated NaNO3 solution containing 46.8 g. N a S 0 3 per I O O g. replaced t h e water in t h e above was saturated with 3.24 g. N a N 0 3 work, a n d t h e "03 per I O O g. of t h e original 40' Be. acid, a n d all work was conducted a t 1 5 ' C., not permitting t h e temperature at a n y time t o go below 15' C., i t was found t h a t each addition of nitrate solution caused a separation of solid N a N 0 3 . Eventually N a N 0 3 h a d b e e n , added t o t h e extent of 4.8 per cent of t h e 40' BC. acid taken, a n d t o bring t h e sp. gr. back t o 40' BC. there had been 8.3 per cent of water or a total addition of 13.1 per cent of t h e weight of t h e 40' BC. "03 used t o dissolve N a N 0 3 . T h e dilution of t h e NaN03-HN03 mixture was carried out in steps which may be summarized as follows a t t h e end of each dilution with its accompanying N a N 0 3 crystals separation. TABLE11-HNOs STRETCHING WITH NaNOs AND WATERAT 15' C. Total Addition per 100 G. Original 40' BC. "Os NaNOs-"08 -DILUTIONMixture I I1 I11 NaNOsinsolution 3.24 3.45 4.15 A.83 Water in NaNOa solution.. 0 .OO 2.04 5.67 8.30 Total added matter 3.24 5.49 9 . 8 2 13.13 Sp. Gr. at this dilution.. 1.3g9 1.3:4 1.3$6 1.3$0 Be. equivalent.. 41.4 41.0 40.4 40.0
.................... ............ ................... .............. .....................
Curve I V illustrates t h e gain in NaN03 content with falling density of mixture due t o dilution with N a N 0 3 solution a n d Curve V shows t h e rate of total gain in weight b y diluting with NaNO3 solution.
A similar series of results was accumulated at higher (ordinary) temperature as more practical working conditions. T h e y may be summarized as follows : T h e sodium nitrate solution used for dilution contained 48.33 g. nitrate, per I O O g. solution, and its sp. gr. was 1.399 a t 22.5' C. Separation of N a N 0 3 crystals took place in each case upon using this solution for diluting t h e nitric acid-sodium nitrate mixture. STRETCHINGWITH NaXOa AND WATERAT 22.5' c. Total Addition per 100 G. Original 40° Be. "03 NaNOs-"0s -DILUTIONMixture I I1 .~ 3.96 4.26 5.08 NaNOs in solution., 0.00 1.95 5.53 Water in NaNOs solution.. 3.96 6.21 10.61 Total added matter.. 1.3!8 1.3!1 Sp. Gr. a t this dilution.. ................ 1.3:2 BC. equivalent 40.8 40.5 40.0
TABLE III-HNOs
..................... .............. ...................
.........................
Curve V I illustrates t h e gain in weight a n d rise in density at 2 2 . 5 ' C. when N a N 0 3 is dissolved in 40' BC. "0,; Curve VI1 illustrates rise i n N a N 0 3 concentration with falling density due t o dilution with
T H E J O 1-R X A 4L O F I S D r S T RI-4 L -4 S D E-VGI N E E RIA'G C H E X I S T R Y
Aug., 1917
N a S O , solution; a n d Curve VI11 gi\-es rate of total gain in weight b y this dilution.' Sodium nitrate is aery soluble in dilute nitric acid. Actual experiment showed t h a t 12.9 weight parts of 42' B6. acid (sp. gr. 1.408) plus 116.1 weight parts of water had a sp. gr. of 1.037 a t I j ' C. This solution after saturation b y warming with excess sodium nit r a t e a n d cooling t o ~ j C. " had a sp. gr. of 1.366 (38.9' Be.)and a N a N 0 3 content of 70.94 g. per IOO g. of original diluted acid. I n other words, I p a r t of 42' B4. acid plus 9 parts of water and 7.1 parts b y weight of NaNO3 give a solution of sp. gr. of 1.366 (38.9' Be.),or I lb. of 12' Be. acid would make 17.1 lbs. of this mixture. Curve I X represents empirically t h e falling gravity, with t h e addition of goo per cent of water t o 42' BC. acid and Cur\-e X in t h e same way represents t h e rise in density (gain in weight) with the solution
rnBCEFtT
.vAn=*
*o
W.YO,
W E D
of 710 per cent of S a N 0 3 . Curve X I on behavior of 40' B6. acid is drawn in for comparison of t h e possibilities as t h e acid used becomes more dilute. I t had really initiated a t 42' and is, therefore, so shown, otherwise it is identical with Curve 111. POSSIBILITIES r S I S G
SODIUM K I T R A T E S O L U T I O N S
Since agitating a n d heating are desirable when dissolring sodium nitrate in nitric acid a n d as doing so would require special equipment, such equipment and some difficulties might be eliminated if nitrate were used as a strong or saturated solution, instead of as a solid. Using C. P. nitric acid a number of solutions were prepared of I O , 30. 40 and jo per cent strength determined b y specific gravity or as high as 3 j 0 Be. 9 strong solution of sodium nitrate m-as also prepared a t I j '. I t s sp. gr. 75-as 1.3 7 j and i t contained 46.119 g. sodium nitrate per IOO g. solution or 62.721 g. per I O O cc. of solution. Starting n-ith t h e same 7-olume of nitric acid, I O cc. in each case, as t h e sodium nitrate 1 Although these results amply confirm those in Table I, in this series of experiments the total added matter is loiver than was expected. Such reversals of direction, though never serious, and also other interesting solubility phenomena were frequently encountered and the field is a n interesting one for further study, had one the opportunity. Difficulty in making nitrate solutions t h a t were fully saturated and of avoiding supersaturation even in presence of excess salt was striking a t times. No effort u.as made t o insure t h a t solutions were saturated. They were merely made strong and care taken t o avoid supersaturation as far as possible. I n this particular case, as would be expected, more h7aN0s dissolves in 40° BC. "08 a t 22.5' than a t 15' b u t the specific gravity is lower in the warmer case. This prevents, therefore, the addition of as much diluent as in the case d t h less N a S O s dissolved but 174th higher density.
773
solution was added t h e specific gravity rapidly increased until t h e quantity of sodium nitrate was somev h a t greater t h a n t h a t of t h e nitric acid, when t h e specific gravity changed b u t slightly, approaching, b u t never reaching, t h e specific gravity of t h e original sodium nitrate solution. The highest gravity obtained rras about 39.2' Bb., or 1.371 sp. gr., or not quite as high as t h e solution of sodium nitrate itself, 1.37j or 39.6' Be. This was for t h e reason t h a t in every case Rith these strengths of acid. exress sodium nitrate crystallized out upon addition of t h e nitric acid or t h e acid acted merely as a diluent as far as specific gravity of saturated sodium nitrate was concerned. S o analyses of t h e resulting solutions were made in these cases. Record was kept merely of t h e initial quantities used and the resulting specific gravities. Without taking u p space with t h e details of t h e d a t a the Curves X I 1 t o XV give a n idea of t h e tendency of strong N a N 0 3 solution t o boost t h e specific gravity of t h e weaker nitric acid under this set of conditions. These general conclusions were sustained even when stronger acid, j4.4 per cent, sp. gr. 1.343, or 37' BC. was treated with progressive amounts of a stronger solution of NaKOs of sp. gr. 1.392 and NaXOs cont e n t of 46.8 g. per IOO g. solution. beginning with smaller amounts of nitrate t h a n previously mentioned. I t was found t h a t for each IOO g. of acid, 5.1 5 g. of nitrate solution gave a sp. gr. of 1.348. Upon t h e addition of 10.2 g. nitrate solution, separation of sodium nitrate commenced and t h e highest specific gravity was ob: tained, 1.3j 2 . Progressive additions of nitrate solution were accompanied b y continuous elimination of solid sodium nitrate and t h e specific gravity fell constantly as may be seen from Table IY. N o determination of t h e concentration of nitrate in t h e resulting acid mixture was made b u t merely record kept of t h e progressive change in density after definite addition of nitrate solution. TABLEIV-SPECIFIC
GR.4VITY
COMPARISONS
OF V A R I O U S &fIXTURES O F
(SP. GR 1343) A N D SATURATED S a x 0 3.~(SP GR 1392) Sp. Gr. NaN03 Solution Total NaSOa Solution of Added per 100 G. .4dded per 100 G. Mixture Original " 0 3 Original HNOa 1.343 000.000 000.000 1.344 1.024 1.024 1.348 4.126 5.150 5.052 10.202 1.352(a) 15.263 25.465 1 .342(b) 26.60 1.324 52.07 54.63 1.311 106.70 107.53 1.316 214.23 220.5; 1.339 434.80 332.12 1.357 766.92 [ a ) Crystallization began. ( b ) Check on this point was as follows: Sp. gr. 1.352+; NaN03 solution added per 100 g. Hh-03, 10.287. N o crystallization resulted upon addition of a small crystal of Nah-08 and allowing the mixture t o stand 12 hrs. a t 15 t o 20° C. HS03
~~
~I
Curve X V I shows graphically t h e increases and breaks in t h e specific gravity caused b y t h e addition of strong K a N O B solution t o HxOs under t h e above conditions. Using still stronger acid, t o a strong solution of sodium nitrate (sp. gr. 1.326 a t I j " C.) containing 40.8 g. salt per I O O g. of solution, was added 28 parts b y weight of 42' B4. nitric acid per 131.8 parts of nitrate solution. This solution was allowed t o s t a n d 48 hours in contact with a crystal of sodium nitrate. -4 crop of about 4 g. of good nitrate crystals was obtained, t h u s preventing supersaturation. The orig-
7 74
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
inal acid had a sp. gr. of 1.408;t h e sodium nitrate solution a sp. gr. of 1.326; t h e final mixture stood 1.336 or 36.5' BC. at 15' C. This final solution contained 32.6 g. of sodium nitrate per I O O g. of t h e solution plus 17.73 parts by weight of 42' BC. H N 0 3 a n d 49.67 parts of water exclusive of t h e water present
Vol. 9, No. 8
SULFATE A N D ACID S C L F A T E ADMIXTURE
The separation of nitrate crystals from nitric acid is by no means evidence t h a t nitrate h a d been mixed with or added t o t h e acid. T h e solution of sodium sulf a t e in strong nitric acid was found t o deposit small white crystals which are clear cut rhombohedrons of sodium nitrate. This behavior might be expected f r o m general considerations a n d in connection with t h e possibilities of t h e following equation: Na2S04
+ H N 0 3 = NaHS04 + N a N 0 3
The original admixture might have been, therefore, sodium sulfate and still have sodium nitrate separate from t h e acid. Nitric acid (sp. gr. 1.381,40' Be.) was found t o dissolve 12.62 g. of sodium sulfate per I O O g. of t h e acid a t 15' C., giving a sp. gr. of 1.416or 42.6' BC. This was diluted. with water in steps t o 40' BC. with results as follows: STRETCHINGWITH NazSO4 AND WATER AT 15' c. Total Addition per 100 G. Original 40' BC. "01 NalSOeHNOs -DILUTIONMixture I I1 I11 NalSOc in solution.. .............. 12.62 12.62 12.62 12.62 0.00 2.31 7.91 15.15 Water in NazSOi solution.. Total matter added.. 12.62 14.93 20.53 27.77 Sp. Gr. at this dilution.. 1.416 1.4;O 1.3902 1.3z4 BC. equivalent.. ................. 42.6' 42.2 40.8 39.5
TABLEV-HiYOs
........ ..........
.............
in t h e 42' BC. nitric acid, or I part of 42' B&. "03 per 1.837parts N a N 0 3 and 2.79 parts of water. Curves XVII a n d XVIII show t h e gain in both NahT03 a n d water, respectively, during dilution with t h e NaKOI solution. T h e 42' BC. acid used contained 18.8 g. of real "03 and t h e final product (36.5' Be.) has a specific gravity corresponding t o 83 g. of real " 0 3 or a gain on this basis of over 340 per cent. This apparent gain was produced b y adding less t h a n 2.7 lbs. of sodium nitrate per lb. of original 42' acid. Using a smaller quantity of strong acid, t o I O O g. of a water solution of N a N 0 3 (sp. gr. 1.393 or 41' BC. at IS") was added 2.56 g. H N 0 3 (sp. gr. 1.408 or 42' Be.). After standing for 24 hours at room temperature the solution was cooled t o 15' C. a n d de-
I t - w a s also found t h a t t h e addition of sodium sulfate t o 40' Bi..nitric acid could raise i t t o 45' BC. Sodium acid sulfate separates apparently as such, together with some sodium nitrate when added t o nitric acid. This acid of 40' BC. strength was found t o dissolve 12.62 g. of sodium acid sulfate per I O O g. of t h e acid a t I j " C., giving a sp. gr. of 1.462 or 45.8' Be. This was diluted in steps with water t o 40' BC. with t h e following results:
canted f r o m t h e crystals which h a d precipitated. T h e sp. gr. of t h e solution at this point was 1.386, or 40.5' BC. The N a N 0 3 content of a saturated water solution This of N a N 0 3 is 47.430 g. per I O O g. of solution. means t h a t our 3900 per cent of sodium nitrate solution added t o 42' BC. "03 gives a mixture of 40.5' BC.
TABLEVI-HXOa STRETCHING WITH NaHSOa AND WATER AT 15' c Total per 100 G . Original 40° Be. "Os NaHSOi-HNOs ---DILUTIONMixture I I1 I11 12.62 12.62 12.62 hTaHSOd in solution., ............. 12.62 16.36 26.68 2.89 Water in NaHSOi solution. . . . . . . . 0 . 0 0 28.98 39.30 15.51 Total matter added.. ............. 12.62 1.4;2 1.3!2 1.45: Sp. Gr. at this dilution.. .......... 1.462 42.3 40.0 45.4 €36. equivalent.. . . . . . . . . . . . . . . . . . 45.8'
These results could very easily be obtained in using t h e nitre cake from t h e manufacture of nitric acid. This material is at hand and convenient a n d is a drug on t h e market at present. It is interesting t o note t h a t t h e solubility of sulfate a n d acid sulfate is t h e same in this strength acid if equilibrium actually was ob-
Aug., I917
T H E J O U R X i l L OF I N D C S T R I A L A N D E Y G I Y E E R I N G C H E M I S T R Y
tained in both cases. Confirmatory work on this b y different persons arrived at t h e same conclusions. I n spite of this, however, t h e specific gravity is different in t h e case of t h e solutions of these two salts and, therefore, much more water can be added in t h e case of t h e acid sulfate without lowering t h e specific gravity below 40' BC. Curves X I X , SasSOh, and X X , S a H S 0 4 , illustrate clearly t h e real danger t o t h e consumer from t h e presence of even a little acid sulfate in his nitric acid. I t s effect on t h e density is profound and a comparison with t h e effect of K a N 0 3 (Curve I11 superimposed)
is edifying. It was interesting t o note t h a t the curve for Nan.0, (111) lay exactly on t h a t for S a H S 0 4 ( X X ) as though N a x O s went into solution as a n acid nitrate, for n'aHS04 could hardly go into solution as a nitrate. FISASCIAL BEARIKG
Enough results have been given t o indicate t h e possibility of profitable sophistication of nitric acid and a t any rate t o warn against serious loss t o consumers. T h e indication of a few financial possibilities will suffice t o point out clearly t h e dangers of these opportunities for salt admixture in commercial acid. Our contract called for "Aqua Fortis 40' Pale" at 9 cents f . 0 . b. (9.5 cents delivered). The O i l , P a i d aiid DriLg Reporter's quotations, June 19, 1916, were as follows: !qua
36 38: 40 42'
Fortis !1/2--T3,'4 13/4-8
S i t r a t e of Soda $3.10 per cwt. spot
8 -81j'4 81/4-8'/2
These are, of course, war prices. ing quotations, June I:, 1912, were: Aqua Fortis
36' 38' 40' 42'
Salt Cake (July 3) 70 c. per cwt.
35/k41/2 4 -41/4 41/4-43/r 4'/e-S
Nitrate of Soda $2.45 per cwt.
The correspondSalt Cake 55-65 per cwt.
Nitric acid is quoted from a fraction to a full cent higher for t h e various strengths. If cost of materials are figured in t h e case where 40' BC. "03 dissolved 3.24 per cent of its weight of N a N 0 3 a n d then permitted t h e addition of 6.0 per cent of water before t h e gravity fell t o 40' BC. again, we reach t h e following statement:
775
Buying always at t o p market a n d expecting on sale only bottom market, 100 lbs. 40' BC. Aqua Fortis a t 81,'~ c.. ........................... 3.24 lbs. PITaSOs a t 3.1 c.. 6.0 lbs. water.. . . . . . . . . . . ................. Total 109.24 lbs. 40' Be. mixture costing.. ....................... 109.24 lbs. 40' BC. Aqua Fortis a t 81/4 c. brings
$8.25
8.35
Xlinimum Margin t o producer p Minimum Excess (dead loss) paid by consumer a t 8 c.. . . . . . . . . . . . . 0 . 4 9 per 100 lbs. purchased., . . . . . . . . . 0.45 Minimum Excess a t ante-bellum prices per 100 lbs. purchased a t 43/4 c. 0.40
There would have been no excess paid by purchaser under extreme minimum condition a t 41/4 cents in ante-bellum times. I n t h e case of the d a t a where 40' BC. acid saturated with NaXO3 permitted t h e addition of T\;aNO3 solution t o such a n extent t h a t a N a N 0 3 total of 4.8 per cent of t h e weight of t h e original 40' B6. " 0 3 had been added and a n addition of 8.3 per cent of water or a total of 13.1 per cent before 40' B6. was again reached, we have t h e following situation: 100 lhs. 40' Be. Aqzia Fovlis a t 81, 4 c 4.8 lbs. S a x 0 8 a t 3.1 c.. . . . . . . . . . . . 8.3 lbs. water.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.1 lbs. 40° BC. mixture costing 113.1 lbs. 40' Be. Aqua Fortis a t 8'/a c. brings.. . . . . . . . . . . . . . . . . . . a t 8 c. brings.. . . . . . . . . . . . . . . Xinimum Margin t o producer per 100 lbs. initial a c i d . . . . . . . . . . . . . . Minimum Excess (loss) paid by consumer per 100 Ibs. purchased a t 8 c. Minimum Excess a t ante-bellum prices per 100 lbs. purchased a t 41;4 c. hIinimum Excess a t ante-bellum prices per 100 lbs. purchased a t 4314 c.
$8.25 0.15
.... 8.40 9,33 9.05 0.65 0.70 0.05 0.54
Cost of materials follows for t h e case where 42' H x O 3 was diluted with 9 parts of water and then saturated with 7.1 parts of N a N 0 3 , giving a total of 1 7 . 1 parts of a mixture with specific gravity 1.366 or 38.9' Be. 1001hs. 42' Be. Aqua Fortis a t 81,'2 c . . . . . . . . . . . . . . . . . . . . . . . . . . . T10 lbs. Sa?;Oa a t 3.1 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900 lbs. water ..... Total 1710 lbs. 38.9' Be.mixture costing.. . . . . . . . . . . . . . . . . . . . . . 1710 lbs. 38' Be.Aqua Fortis a t i 3 / 4 c. brings.. . . . . . . . . . . . Minimum margin to producer per 100 lbs. initial acid.. , , . . , . , , . . Xinimum Excess (loss) paid by consumer per 100 lbs. purchased a t 7',/4c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Xinimum Excess a t ante-bellum prices per 100 lbs. purchased a t 4 c.
3
8.50 22.01
30.51 132.53 102.02 7.28 3.70
This is a margin over cost of materials of $ 1 0 2 . 0 2 on a n investment of $30.51, b u t it will be noticed t h a t t h e margin is really greater t h a n this for t h e mixture n-as 38.9' Be.,and i t could stand much more dilution before it reached 38' Bb.,t h e acid quoted a t i 3 / 4 cents, and this would materially increase t h e margin derived above. The consumer in purchasing 1 7 1 0 lbs. really received b u t I O O lbs. of 42' H N 0 3 equivalent t o 1 2 0 lbs. of 38' BC. acid which should have cost him $9.30 t o $9.60 instead of $132.53. I n normal times, with prices as quoted, t h e margin over cost of all materials would be $46.00 per I O O lbs. of 42' Be. acid invested, and t h e consumer would pay $68.40 for acid whose cost should not have been above $5.00.
Cost of materials follows for t h e case where 42' H N 0 3 was mixed with 1.97 parts of N a N 0 3 and 3.13 of water, giving a solution with a specific gravity of 1.336 or 3 6 . j ' BC.
T H E J O U R N A L O F I N D U S T R I A L A N D ELVGINEERING C H E M I S T R Y
776
Vol. 9 , KO.8
L
100 lbs. 42’ Be. Apua Fortis a t
at
7’/2
c.. ...........
c.. .......................... .............
$8.50
.........................
$4 6 . 1 0
81/2
s (J6,’s c.) per 100 lbs. pur-
.................... ”03 was mixedlwith 1 2 . 6 2 parts Na?SOr and parts of water, giving a 40’ BC. solution.
2.80
1j.Ij
100 Ibs. 40’ B&.?AquaTFovtis a t S1,’r c.. . . . . . . . . . . . . . . . . . . . . . . . . . . S 8.25 0.09 12.62 lbs. NaaSOa a t 0.7 c.. . . . . . . . . . . . . . . . . . . 15.15 lbs. water .................................. Total 127.77 lbs. costing.. . . . . . . . . . . . . . . . . . . . . . . S 8.34 s a t 8 c. brings.. . . . . . . . . . . . . . . . $10.16 Minimum margin t o producer per 100 lbs. initial acid., . . . . . . . . . . . S 1 . 8 2 Minimum Excess (loss) paid by consumer per 100 lbs. purchased a t 8 c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.51 Minimum Excess a t ante-bellum prices per 100 lbs. purchased a t 41/4 c ...................................... 0.51
I n t h e case where N a H S 0 4 (nitre cake) was used t h e total matter added was much higher t h a n in t h e case of sodium sulfate without lowering t h e gravity below 40’ BC. T h e margin t o t h e producer would be greater, therefore, t h a n with t h e normal sulfate a n d particularly so since nitre cake is a drug on t h e market a t present with most acid makers a n d usually is with many of them. DISCUSSIOS
With these quotations i n . m i n d i t is evident t h a t i t would be profitable t o buy 4 2 ’ acid a t t h e t o p price, or 5 cents in war or normal times, respectively, a n d a d d t o it sodium nitrate or a strong nitrate of soda solution or either of t h e sulfates of soda in such a way as greatly t o stretch t h e amount of acid on h a n d b y diluting with water, and selling a t even t h e lowest quotation for t h e particular specific gravity obtained. Not as much salt a n d water need be present as in t h e extreme possible cases cited. The profit t o t h e producer a n d t h e loss t o t h e consumer can be of any size short of t h e maximum. I t has been shown b y t h e d a t a given t h a t even a casual boil-over of NaHSO1 during distillation may entail a n unnecessary loss t o t h e consumer by unduly increasing t h e producers’ yields a t t h e expense of t h e consumer. Even I cent per pound is a severe raise on t h e market in t h e case of 9 cent acid and may spell disaster t o many operations. I t seems likely t h a t no fraud was intended in t h e case which caused this investigation and, therefore, t h e name of t h e manufacturer has been withheld even in private conversation. Further deliveries, however, were refused. It would seem t h a t t h e presence of t h e sulfuric radical in t h e nitrate separating from t h e acid shows either large amounts of sulfuric acid in t h e nitric acid or t h e results of a boil-orer of nitre cake or “soup.” The fact t h a t t h e acid always arrived of t h e correct specific gravity does not signify intentional adulteration, for t h e final correction of t h e specific gravity might be made b y a n employee who had no knowledge t h a t a boil-over had occurred. T h e presence of SOa in reagent (“pure”) “ 0 3 has been long known though no commercial informa-
tion is published. I n one case1 the manufacturer suggested t h a t i t came from the “salt cake” used i n makirig the bottles irt which the acid w a s stored. I t is unlikely t h a t adulteration of commercial acids is practiced t o any extent. Obviously no reputable manufacturer would avail himself of t h e possibilities indicated in this paper. However, these possibilities must be kept in mind by consumers for even operating employees might a t times fall t o t h e temptation t o better their yield record in this way. T h e possibilities herein disclosed of varying amounts of contamination in commercial nitric acid are not of direct financial significance merely, though t h a t phase is serious enough, for i t is evident t h a t t h e presence of salts in quantity may seriously impede processes as well as curtail yields of same. This last effect may be quite serious where t h e nitric acid failure even t o t h e extent of a few per cent in one operation may cause a greatly magnified fall-off in t h e finished product, leaving all question of quality out of consideration. It should be noticed by consumers of most commercial acids such as hydrochloric, sulfuric, and acetic, t h a t similar possibilities exist in these cases. The solubility of salts in some of these is even greater t h a n in t h e case of nitrates a n d with some of t h e m little or no inspection is exercised other t h a n specific gravity determinations. Obviously t h e determination of t h e acid radical in most cases would give little protection and titration is not satisfactory with some of them. A n evaporation test for residual salt would be t h e only certain single test t o eliminate t h e factor under discussion. The author wishes t o t h a n k hlessrs. F. R. Porter, W. J. Becker, H. hIersereau, S. L. Shenefield a n d T. A. Boyd for checking d a t a b y laboratory experiment a t different times. c o s c L u s I o ~ s
I-The strength of commercial nitric acid cannot be derived with safety from t h e specific gravity alone nor from t h e specific gravity and NO3 content alone but titration will be necessary in addition provided always t h a t sulfuric acid is found t o be absent b y qualitative tests. It seems desirable t o combine a specific gravity or NO3 determination with an evaporation test for residual salts. 11-Producers and consumers alike should inspect all commercial acids by a n evaporation test. LXBORATORY OF IKDUSTRIAL CHEMISTRY THE OHIO STATE UKIVERSITY
COLUXBUS, OHIO
DETERMINATION OF THE EXPLOSIBILITY OF PYRITES AS WELL AS ITS AVAILABLE SULFUR AND THE SULFUR CONTENT OF ITS CINDERS By C. R. GYZXKDER Received May 16, 1917
I n buying pyrites as a source of sulfur in sulfuric acid manufacture, high content of sulfur in t h e ore is not necessarily a guarantee for its fitness, since other characteristics have a bearing on t h e amount of sulfur available for t h e production of sulfur dioxide. Thus, 1
C h e m . S e w , 61, 289 and 301.
