Nov., 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
Barium sulfate becomes more soluble in strong sulfuric acid, as is well known, and an acid sulfate forms from strongly acid solutions. N aaSOd-( NH4)zS04-HzO This system has recently been well investigated by Matignon and Meyerl through a considerable range of temperature. The work is of importance a t present because of the possibility of using niter cake t o absorb ammonia and produce ammonium sulfate. The attempts which have been made t o do this have been summarized by Johnston.2 They appear not t o have been very successful thus far and the results obtained have been irregular. With the data which have now been published, i t is possible t o calculate exactly what can be done in this direction. A double salt, NazS04. (NH4)2S04. zHz0, forms, with a transition temperature a t 59'. Above this temperature, only the single salts are deposited from solution. r\:azS 04-RS 04-HzS 04-Hz0 N o four-component system of this type has been thoroughly investigated. D'Ans has given a few d a t a for solutions containing calcium sulfate. An investigation is in progress in this laboratory on such a system containing copper sulfate. It is t o be hoped t h a t investigators elsewhere may work out the d a t a for other sulfates. The problem is an interesting one from a scientific standpoint as well as pointing out possible uses for niter cake.
89 7
1.5H20, and NaH3(SOd)~. Of these we may discard the last three, since their removal from solution takes out too much sulfuric acid. Further, NaaH(SO4)z. Ha0 need not be considered since it rarely forms. The d a t a of D'Ans, expressed in per cent of solution by weight, are given in Table I together with the composition of each solid phase considered. TABLS I
SOLUBILITY AT 25' ----SolutionSOLIDPHASES HzSOa NazSOi Hz0 NazSO4.iOHzO.. 0.00 21.90 78.10 59.26 8.67 32.07 NazSO~.10HzO~NazSO~ 34.64 49.02 16.34 Na2SOaeNasH(SOa)s.. N a s H ( S O a ) z ~ ' N a H S O ~ . H z.... O 30.60 30.05(a) 39.35 56.49 6.68 36.83 NaHSO4.HzO~NaHSO4.. ComDosition of Salts 44,lO 55.90 NazSOa.IOHz0.. ................ 0.00 18.70 81.30 0.00 NasH(S0a)z ..................... 35.50 51.46 13.04 NaHSOi.Hz0 40.83 59.17 0.00 NaHSO4 (a) Determined by H. W. Foote. D'Ans gives 26.30.
................
.......
.......
....
................... .......................
These solubility data are also plotted in the figure. Straight lines have been drawn between the points representing the univariant systems and the calculations are based on this approximation. Here also are shown lines radiating from the origin representing the composition of niter cakes of 2 0 , 25, 30, and 35 per cent sulfuric acid, also similar lines for the two acid I
I
I
I
I
I
I
I
I
SHEFFIELD CHEMICAL LABORATORY YALEUNIVERSITY NEW HAVEN,CONNECTICUT
THE RECRYSTALLIZATION OF NITER CAKES By BLAIRSAXTON Received July 24, 1918
I n this paper the solubility d a t a of D'Ans4 for 25' and of Pascal2 for o o will be used t o calculate in some detail the extent of the separation of niter cake into its constituents which can be effected by leaching or crystallizing a t these temperatures. The data of D'Ans are very good. Unfortunately Pascal has expressed his results in a triangular diagram only and data scaled from this are not reliable. Calculations have been made for o o , however, and they are valuable in showing t h a t the separation can be made more efficiently Solubility detera t t h a t temperature than a t 25'. minations for temperatures lower than 25' are in progress in this laboratory and then the possibilities a t these temperatures will be considered. Calculations somewhat similar t o these which follow have recently been made b y Hildebrand' and Blasdale.6
sulfates, N a ~ H ( f 3 0 4 )and ~ NaHS04. HzO. The intersection of one of these lines with the solubility curve gives the composition of solution which will first become saturated with the solid phase represented by t h a t branch of the curve intersected. This of course tells what solid will form first on crystallizing a t 2 j For instance, i t shows t h a t a niter cake which is 2 5 per cent sulfuric acid is never saturated with the decahydrate; hence it never forms on crystallizing.1 Considering the lines of the diagram as straight and letting x and y represent the concentrations of sodium sulfate and sulfuric acid, respectively, in saturated solution, the equations for these lines become as follows: CRYSTALLIZATION AT 2 5 O A B , % = 21.90 1.173 y At this temperature we may crystallize the following BC, x = 2 9 . 1 7 0.335 y solids: NazS04. IOHZO, Na2S04, NaaH(SO4)2.HzO, CD,x = 39.90-0.322 y ' Na3Fx(so,),, NaHS04.Hz0, NaHS04, N ~ H g ( s 0 4 )-~ . DE,% = 57.67- 0.90'3 y 1 Comfit. rend., 166 (1917), 787; 166 (1918), 115.
'.
+ +
a LOG. cit.
Published at the request of the Division of Chemistry and Chemical Technology of the National Research Council. 4 LOG.ciL, preceding article. 6 THISJOURNAL, 10 (1918), 96. 6 Ibid., 10 (1918). 347. 8
1 The point of saturation can also be calculated by solving two simuL taneous equations: one, the equation for a branch of the solubility curve; the other, the equation for the line showing the composition of the niter cake or solute. The line AB in the diagram is represented by the equation x = 21.90 4- 1.173 Y. A 20 per cent acid niter cake is represented by the equation x = 4 Y. On solving these we obtain x = 7.75 and y = 31.00.
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 E N G I N E E R I N G C H E M I S T R Y Vol.
89 8
Given these equations and the composition of t h e solute before crystallization, i t is possible t o calculate t h e weight of the solid separating and the composition of the residual solution. For instance, let us consider the solid crystallizing t o be Na2S04. If we represent the weights of sodium sulfate a n d sulfuric acid in solution before crystallization as n and s, respectively, and the amount of Na3SO4 separating from solution as z , then a t any point along BC t h e following relation must exist: 1zz 0.335~ - x - 29.17
+
S
and, solving for z, z
Y
=
Y n-
s (0.335
+ T29.) I,7
z = 87.3-
w
IO,
No.
11
744.8 0.8732 y-
7.461
(35.0-0.187~)
~- 0.678) (60;ro If we know t h e value of both x and y for the solution in equilibrium with a given solid, we may avoid using these general equations. Again, starting with I O O g. of 35 per cent acid niter cake, we may calculate the makimum amount of Na3H(S04)2 t h a t can separate b y using t h e d a t a for t h e point D in the diagram. This gives us 65.00- 0.8132 - _ _ _ - 30*05 = 0.982, 30.60 3 5.00 - 0 . I 87 z =
from which z becomes 48.66. Then the weight of sulfuric acid left in solution, 3 5.00 - 0.187 z, becomes 25.90. This is the type of calculation which has been Z = C - CS (0.01335 f 0.2917 used mostly in this paper, since it tells us the most we can do in separating a n y one solid phase. Hence in Y speaking of crystallizing Na2S04. 1oHz0, Na2S04, If t h e solid separating is NaaH(SO4)2, the value of z Na3H(SO&, or iVaHS04.H20, we refer t o crystallizing is calculated by means of a similar equation, Le., each to t h e points B, C, D, and E, respectively. If, n-0.813~ however, a specific use of niter-cake solution requires - 39.90-0.322~ s - 0.187z Y a certain acid concentration, one can tell from t h e Hence we are able t o calculate how much of a n y solid figure what will first crystallize, and calculate how will separate if we know the composition of the niter much will separate, and how much sodium sulfate and cake or the solution from it, and the per cent of sulfate sulfuric acid will be left in solution b y using the general acid in solution after crystallization. equations. Further, we can calculate the weight of water in I n separating niter cake into its constituents either the solution after crystallizing, or, which amounts t o b y leaching or crystallizing a t 25' we have the followthe same thing, the amount of water t o be added t o ing possible processes which may be used separately the solid niter cake in leaching at 2 j o in order t o leave or combined: z grams of one of the solid phases. If we are evapo(A) Remove NazS04.10Hz0 from solution. This rating the solution instead of leaching the solid, this may be done b y evaporating the solution t o a calcuweight of water added t o c, the weight of t h e cake, lated weight, or just t o an acid content of 8.67 per will give the weight t o which the solution must be cent, or by leaching completely with the calculated evaporated, except when the solid separating is a amount of water. The solute (sodium sulfate sulhydrate, in which case the total weight is the sum of furic acid) will then be 2 1 . 28 per cent acid. Of t h e the weight of the solution-sodium sulfate, acid, niter cakes here considered only t h e one which is 2 0 water, and z . The extent t o which the evaporation per cent acid can deposit this salt at z 5'. must be carried can also be very easily controlled by (B) Remove Na2S04 from solution. This can be testing the acid concentration of the solution. Again done exactly as A. The acid content of t h e solution considering the solid separating to be Na2S04,w , the at crystallization, however, will be 16.34 per cent. weight of water may be calculated as follows: The solute will be 3 2 . o 5 per cent sulfuric acid. (C) Remove Na3H(S04)2from solution b y processes similar t o A and B. The concentration of sulfuric acid in t h e final solution should be 30.60 per cent, and in the solute, 50.45 per cent. (D) Recrystallize t h e NaSH(S04)z from C b y first o r if c is the weight of t h e niter cake or solute-and s removing i"l'a2SOc by process B and then crystallizing its acid concentration, Na3H(S04)2 from the filtrate. I O O g. Na3H(S04)z 0.7083 when thus treated will give 41.66g. Na2S04b y evap0 . 0 1 33 5 ) orating t o I j6.I g. or leaching with 56.I g. of water. Similarly, general calculations can be made for each The filtrate will then deposit 33.81 g. NaaH(S04)~ of t h e other solid phases. The results for those phases when evaporated t o 74.2 g. The solution will then which are here considered are assembled in Table 11. contain 1 2 . I 5 g. of sodium sulfate and 12.38 g. of The equations are much simplified for a n y given acid. The end result in concentration is the same as value of s. For instance, if we take a solution of I O O C, but I 2.38 g. of sulfuric acid have been recovered in g. of a 3 5 per cent acid niter cake which deposits solution which otherwise would be in solid Na3H(S04)2. crystals of Na3H(S04)2first on crystallizing a t 2 5 ' ) we The result of recrystallizing any amount of Na3H(S04)2 find t h a t since s = 35 and G = 100, in this way can be calculated from these data. or if we are dealing with a niter cake whose weight is c and which is s per cent sulfuric acid, this becomes:
-)
+
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Nov., 1918
899.
TABLE11
EXPRESSION BOR z
Sarm PHASE NazSOa
......................................
c
- cs
(0.01335 Jr
n - s (0.335
cs (EXPRESSION
0.2917
-
-)
Y
Y
4- 29.17
s
Y
NasH(S0a)z..
................................
1.145
- 0.007765s
(%-
1.335)
Y
- 0.4569 + 8.544 ) 0.8732 y - 7.461 S
(cs
- 18.7 P)
(cs
- 35.5 z)
39.90 s - (0.322S f ? t ) y 7.461 - 0.8732 y NaHSOa.Hz0
.................................
1.197
FOR W
O.7083 - 0.01335)
- 0.6005 S - 0.001165s + 24.51 0.8351 y- 20.47
(-(42.330.4233
0.000973)
Y
57.67 s - (0.903 S $- n)Y (s - 0.355 P) 0.0973 20.47 - 0.8351 y Y n = t h e weight of sodium sulfate in t h e niter cake or solute. c = t h e weight of niter cake or solute. y = t h e per cent of sulfuric acid in solution after crystallization. s = t h e per cent of sulfuric acid in t h e niter cake or solute. w = t h e weight of water in solution after crystallization. B = t h e weight of solid separating.
(E) Remove N a H S 0 4 . H 2 0 from solution by the methods given for A, B, and C. I n this case the concentration of acid in the solute will be 89.43 per cent and in the solution, 56.49 per cent. The only advantage in crystallizing this acid sulfate is t o raise the concentration of acid. By doing this, much of the acid is removed from solution. Some of this could be recovered by recrystallizing, first separating XasH(S04)2 and then NaHS04.H20. I n order to make a good recovery of acid, this would involve too many operations t o be practical. NaHS04.HZO is 35.50 per cent sulfuric acid, 51.46 per cent sodium sulfate, and 13.04 per cent water and corresponds t o a 40.83 per cent acid niter cake. I t s saturated solution may contain as much as 56.49 per cent of acid. Uses may be found for its solution without further treatment. Finally these processes may be combined t o considerable advantage. I n Table I11 will be found such combinations as BCD. This means t h a t Na2S04has been removed from the solution of a niter cake, then Na3H(S04)2has been crystallized from the filtrate, and, finally, this acid salt has been recrystallized and the residual solutions, having the same concentration, have been combined. I n making calculations for these combined processes the writer found i t convenient t o work out the results which, could be obtained with I O O g. of solute for each case and from t h a t data t o make the calculations desired. After completing process B, for example, the solutions will always have the same composition independent of the composition of the original niter cake. The same is true for process C . The data for these two solutions are as follows: After NazS04 has been removed from solution, I O O g. of the solute in the filtrate will contain 3 2.0 j g. of acid and 67.9j g. of sodium sulfate. This filtrate, on evaporation t o 1 2 7 . 2 7 g., will give 57.96 g. of NasH(S04)zand a solution which contains 20.83 g. of sodium sulfate and 2 1 . 2 1 g. of sulfuric acid. After NaaH(SO4)z has"been crystallized from solution, I O O g. of the solute in the filtrate will contain 50.45 g. of acid and 49.55 g. of sodium sulfate. When this filtrate is evaporated to 123.5 g. i t will deposit 92.21 g. of NaHS04. HzO and leave a solution which contains 1 7 . 7 1 g. of acid and 2 . I O g. of sodium sulfate. I n Table I11 are the results of such treatments as have been outlined on I O O g. of niter cake of 20, 2 5 , 30, and 3 5 per cent acid. I n column fouy is given the
)
weight a t final crystallization in any series of processes. If the combined process is BC the weight for C is given, the weight for B having previously been given. If the final process is D, two weights are given, the first being the weight a t which fc'azSO4 separates, the latter t h a t a t which Na3H(S04)2 is removed in the recrystallization of NasH(S04)~. TABLEI11 HzSOn in niter Weight cake Number I t final Per Treatof opera- crystallicent ment tions zation 1 20.0 A 244.3 160.0 B 1 2 79.4 BC 56.5, 2 6 . 8 BCD 4 19.1, 9 . 1 BCDD 6 C' 1 102.6 149.7, 71.2 CD 3 32.4 3 BCE 33.8 7 BCDDE 25.0 B 1 175.0 99.3 2 BC 4 BCD 7016, 33.6 1 C' 112.9 3 CD 125.1,59.5 CDD 5 42.3. 20.1 3 40.5' BCE 190.0 30.0 B 1 RC 2 119.3 BCD 4 83.7, 4 0 . 3 C' 123.1 1 CD 3 100.5, 4 7 . 8 3 BC E 65.1 1 133.3 35.0 C 76.0. 36.1 CD 3 2 63.4' CE 4 78.2 CDE 1 This can be done from t h e original weight given and allowing t o stand a t 25'. will have changed into t h e acid salt a t this
HnSOa reHzS04 HzSOn covered NazSOi in solu- in in solu- left in tion solute tion solid Per Per Per Per cent cent cent cent 8.67 21.28 100.0 7.5 16.34 32.05 100.0 47.0 30.60 50.45 66.2 83.8 88.5 7 8 . 3 30.60 50.45 96.1 7 6 . 4 30.60 50.45 30.60 50.45 1 0 . 3 97.5 30.60 50.45 69.7 8 2 . 9 56.49 89.43 23.2 9 9 . 3 56.49 89.43 33.8 9 9 . 0 16.34 32.05 100.0 2 9 . 3 30.60 50.45 66.2 78.3 30.60 50.45 88.5 71 .O 30.60 50.45 40.0 86.9 30.60 50.45 79.7 73.9 30.60 50.45 93.1 69.5 23.2 99.1 56.49 89.43 16.34 32.05 100.0 9.1 30.60 50.45 66.2 7 2 . 1 30.60 50.45 88.5 $2.7 30.60 50.45 59.9 14.5 30.60 50.45 8 6 . 4 63.6 56.49 89.43 23.2 98.8 30.60 50.45 74.0 60.9 30.60 50.45 91.2 48.2 56:49 89.43 26.0 98.3 56.49 89.43 32.0 9 8 . 0 solution by evaporating t o t h e All NazSOn.IOH20 and NazS04 concentration.
I t is evident from these figures t h a t the way t o proceed with a niter cake of less than 2 j per cent acid in order t o produce a solute and solution which are 50.45 per cent and 30.60 per cent acid, respectively, is t o remove NazS04 and Na3H(S04)2 consecutively from solution, recrystallize the acid sulfate, and combine the solutions (process BCD). This involves four operations and leaves 8 8 . 5 per cent of the acid in solution a n d over 70 per cent of the sodium sulfate in the solid. The recrystallization of the acid sulfate could be repeated, thus recovering 96.I per cent of the acid but i t would mean six operations and hence is hardly practical. If the niter cake is over 2 j per cent acid, Na8H(S04)z can be efficiently separated from t h e original solution, recrystallized, and the solutions combined. This takes only three operations. If the niteicake is 2 j t o 32 per cent acid, the recovery of sulfuric acid will be from 80 t o 85 per cent. If the niter cake is 3 2 t o 50 per cent acid, 91.2 per cent of the latter
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 E N G I N E E R I N G C H E M I S T R Y Vol.
900
will be recovered in solution. At 25' no method for concentrating the acid in solution as far as the point E in the diagram (a solution of 56.4 per cent, and a solute of 89.43 per cent acid) is possible without removing 7 0 to 80 per cent of the acid. Of course N a H S 0 4 .HzO can be removed so t h a t the solution will have any desired concentration represented along the line DE. Proceeding for short distances along D E would not sacrifice an unreasonable amount of acid. I n order to test the practicability of these calculations, experiments were made on the removal of Na2S04 and NaaH(SO)2 from solutions of 100 g. of 3 0 per cent acid niter cake. The solutions were made by warming I 58.7 g. of recrystallized Glauber's salt with 3 I . 6 g. of 95 per cent sulfuric acid in Erlenmeyer flasks. A small amount of anhydrous sodium sulfate remained undissolved. One sample of such a solution, since it weighed 190.3 g., was cooled without further evaporation, corked, and immersed in a thermostat a t 25" for 48 hrs. The NazS04 was filtered through a small suction filter and washed free from mother liquor with the solution recommended by D'Ans, consisting of 50 cc. of water, IO cc. of concentrated sulfuric acid, and 7 5 cc. of alcohol. After removing t h e mother liquor, t h e salt was washed with alcohol and then with ether. When d r y i t weighed 7.0 g., while the amount calculated for t h e point C is 6.4 g. A little NasH(S04)~no doubt separated since the solution analyzed 16.42 per cent sulfuric acid and D'Ans found 16.34 per cent for the univariant point C. A second sample of the solution was evaporated t o 1 2 4 g. and treated in the same way. The calculated weight of the solution a t crystallization is I 23. I g. b u t the last stages of evaporation offered some difficulties since the solution practically solidified. The acid sulf a t e was washed and dried in the same way as was the Na2S04. When dry it weighed 68.5 g., while the calculated weight is 64.4 g. Here again the univariant point was reached, since the' solution analyzed 30.61 per cent acid, while D'Ans found 30.60 per cent. The salt on analysis for sulfuric acid proved t o be pure Na3H(S04)z. Considering the roughness of these experiments, both of them can be considered as satisfactory checks on the calculations. RECRYSTALLIZATION
AT 0 '
The data of Pascal have been scaled from his diagram and are given in Table I V and plotted in the figure. They are expressed in per cent by weight of solution. SOLID PHASES
. . ... . . . .
TABLEI V -SolutionHzSO4
. .. .... ..
NazSOa.lOHz0 . . .. NazSOa.lOHz0 NaaH(SO4)z.. NasH(S01)z NaHS04.HzO.. . . .. NaHSO4.H20 J _ NaHSOa
.
... . . .
0.00
28.14 46.81 61.28
NazSO4 3.68 23.93 5.26 1.84
HzO 96.26 47.86 47.60 36.29
These data are inaccurate as has been pointed out, b u t they are valuable, as the following calculations will show, These calculations have not been carried out in as great detail as those for 2 5 ' because of the data on which they are based.
IO,
No.
II
A t o 0 we have four solids which can reasonably be separated: Na2S04. IOHZO,Na3H(S04)~,KaHS04. H 2 0 , and NaIIS04. Solutions of niter cake of the range of compositions considered in this paper will first be saturated with Glauber's salt a t oo. The removal of this alone is very effective. It will leave all the acid in solution and the concentration of acid in the solution and solute will be 28.14 and 54.04 per cent, respectively. If Na3H(S04)2 is then crystallized from the solution, 8 2 . 6 per cent of the acid will be recovered, the solution will be 46.81 per cent acid, while the concentration of acid in the solute will be 8 9 , go per cent. Recrystallizing the acid sulfate, by removing NazS04. IOHZOand Na3H(S04)z,successively, from its solution, and then combining the solutions will not change the composition of the solution or solute, b u t will recover in solution 97.o per cent of the acid. I O O g. of NaaH(SO4)z recrystallized in this way a t o 0 will give 148.3 g. of NazS04.1oHzO when treated with 114.7 g. of water or its solution evaporated t o 214.7 g. The solution will then separate I 7.43 g. of Na3H(S04)2 when evaporated t o 50.3 g. The final solution will contain I. 73 g. of sodium sulfate and I j.44 g. of sulfuric acid. If higher concentration of acid is desired this may be accomplished by evaporation and removal of N a H S 0 4 . H2O. This also can be done efficiently as can be seen from a glance a t Table V. By removing Glauber's salt, Na3H(S04)2, and NaHS04. HzO, successively, from solution we are able t o recover 77.7 per cent of the acid and obtain, as the result of these three operations, a solute a n d solution of 97.I O and 61.28 per cent sulfuric acid, respectively. From 9 8 . 7 t o gg. 4 per cent of the sodium sulfate in the cake is left in the solid. Any further desired concentration can be effected from this point since there is little sod'ium sulfate left in solution and very little if any of the acid salts can separate and hence little sulfuric acid can be removed. I n other words, the solution now behaves like a solution of sulfuric acid only. T h e results obtained with' I O O g. of niter cake of several compositions are given in Table V. The meaning of the letters in column two is the same as in Table 111. T A B L EV H?SOa In
niter Weight cake Number a t final Per Treat- of opera- crysfallicent ment tions zation 20.0 A 1 213.9 AC 2 53.8 ACD 4 40.0. 9 . 4 ACE 3 27.9 25.0 A 1 210.6 AC 2 67.2 ACD 4 50.0, 11.7 ACE 3 34.9 30.0 A 1 207.4 AC 2 80.7 ACD 4 60.0, 14.0 ACE 3 41.9 35.0 A 1 204.2 AC 2 94.1 ACD 4 70.0, 16.4 ACE 3 48.9
HxSOa in s o h tion Per cent 28.14 46.81 46.81 61.28 28.14 46.81 46.81 61.28 '28.14 46.81 46.81 61.28 28.14 46.81 46.81 61.28
HzSOa reH2so.1 covered NazSO4 in in s o h - left in solid solute tion Per Per Per cent cent cent 100.0 78.7 54.04 97.7 89.90 82.6 89.90 97.0 97.3 97.10 77.7 99.4 54.04 100.0 71.6 89.90 82.6 97.1 89.90 97.0 96.4 97.10 77.7 99.2 54.04 100.0 63.6 89.90 82.6 96.0 89.90 97.0 95.3 97.10 77.7 99.0 54.04 100.0 45.8 89.90 82.6 95.0 89.90 97.0 99.1 97.10 77.7 98.1
It is evident t h a t crystallization or leaching a t o O is much more effective than a t 25' in t h a t greater concentration and recovery of acid can be effected with fewer operations a t the lower temperature. It is inter-
Nov., 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
esting to note in this cqnnection t h a t Wood’ has used a system of cold water percolation in order t o concentrate acid in the solution from niter cake, and t h a t this treatment has been recommended by Prideaux.2 Unfortunately, a t the present time the d a t a are not available for temperatures between the two given. I t may be possible t h a t it is unnecessary t o use a temperature as low as o o in order t o obtain a satisfactory separation. Solubility determinations for this system at 12’ are being carried out in this laboratory by Professor Foote, who suggested this paper t o the writer. I n the preceding paper reference has been made t o the work of Matignon and Meyer on the solubility relations in the system N a 2 S 0 4 - ( N H ~ ) 2 S O ~ - H ~ 0T.h e writer proposes t o treat this system as he has treated the system discussed in the present paper. SUMMARY
General equations have been developed for the system NazSO4-KzSO4-HtO, a t 2j0, by means of which we can calculate how much of a n y one solid phase will separate from a solution if we know the composition of the original solute and the acid concentration of the solution after crystallization. General equations have also been developed for this system a t 2 5 ’ by means of which we may calculate the weight of water in the solution after crystallization, or the weight of water t o be added t o the solid niter cake in order to leave a calculated weight of one of the solid phases. A very simple type of calculation has been applied t o niter cake of several compositions, by which the maximum amount of each solid phase which can be removed from solution a t 2 5 ’ and a t o o has been calculated. Leaching or crystallizing processes have been suggested by which sulfuric acid may be concentrated in the solution a n d sodium sulfate in the solid, a t the two temperatures mentioned. It was found t h a t this separation can be done much more efficiently a t the lower temperature. SHEFFIELD CHEMICAL LABORATORY YALEUNIVERSITY A’EW HAVEN,CONNECTICUT
THE FORMATION OF AROMATIC HYDROCARBONS FROM NATURAL GAS CONDENSATE3
matic hydrocarbons by the thermal decomposition of straight-chain hydrocarbons of low molecular weight. Previous t o this, Bone and Coward’ had passed ethane, ethylene, and acetylene through porcelain tubes a t various temperatures from 500’ t o I O O O O C. and had noted t h a t the decomposition of ethylene gave a black, viscous tar. The quantity of tar was too minute t o admit of analysis b u t they mentioned the fact that a few crystals of naphthalene were noticed also. They hold aromatic formation t o be produced by the breaking down of ethylene t o acetylene from which the aromatic hydrocarbons are produced by polymerization. Pring and Fairlie2 found t h a t acetylene a t high temperatures and in the presence of hydrogen produces methane for the most part, although some ethane was formed also. When ethylene and hydrogen were heated together no acetylene was produced even a t very high temperatures. Methane, however, was produced in large quantities. Jones3 studied the formation of aromatic compounds in coal t a r and is of the op’inion t h a t acetylene plays an unimportant part in the reaction, inclining more t o the belief t h a t the ring bodies are formed directly from olefines with the splitting out of hydrogen. Previous work in this laboratory pointed t o conclusions which were similar t o Jones’, and in a n effort to get a further insight into the reaction the following work was undertaken: It was decided t o divide the work into several parts and investigate each as fully as time allowed, for i t was quite evident from the beginning t h a t any one of the separate fields was capable of large expansion with possible loss of the original aim. The divisions of the work are as follows: ( I ) The effect of catalyzers on the decomposition of straightchain hydrocarbons of low molecular weight. (2) The influence of temperature and of pressure on the production of aromatic hydrocarbons. (3) The formulation of the reaction, Straight-chain hydrocarbons + Aromatic hydrocarbons
By J. G . DAVIDSON
Received May 23, 1918 INTRODUCTION
I n several papers which have appeared recently Zanetti4 has shown t h a t it is possible to produce aro1 J . Sac. Chem. I n d . , 36 (1917), 1216A. a Ibid., 36 (1917), 1216B. 8 This paper is condensed from a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Faculty of Pure Science of Columbia University. The work was begun under the direction of Dr. J. E. Zenetti and is, in part, a continuation of his work. After the summer of 1917, when Dr. Zanetti entered the Chemical Warfare Service, the work was carried on more or less independently although I am glad t o thank Dr. Nelson, Dr. Freas, and Dr. Fisher for their many invaluable suggestions, and without whose help the work could not have been finished. 4 “The Thermal Decomposition of the Propane-Butane Fraction from Natural Cas Condensate,” THISJOURNAL,8 (1916), 674; “The Thermal Decomposition of the Ethane-Propane Fraction from Natural Gas Condensate,” Ibid., 8 (1916), 777; “Aromatic Hydrocarbons from the Thermal Decomposition of Natural Gas Condensate,” Ibid., 9 (1917), 474.
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EXPERIMENTAL
material used was the e t hane-propane fraction of natural gas condensate, supplied in steel tanks under high pressure. The tanks are built on the siphon system, a pipe reaching almost t o the bottom, so the composition of the delivered gas remains almost constant. Analysis of the gas showed it to be composed almost entirely of the two hydrocarbons, although some butane, and possibly some pentane, was also present. No other gases were present in the original material, although tests were made for oxygen, carbon dioxide, olefines, and hydrogen. MATERIAL-The
1
“Thermal Decomposition of Hydrocarbons.” J . Chem. SOC., 9s
11908). 1197.. I ,
“Synthesis of Hydrocarbons at High Temperatures,” Ibid., 99 (1911), 1796. a “Aromatic Formation,” J . Sac. Chem. Ind., 36 (1917), 3 .
