SOflE POINTS IN THE DISTILLATION OF NITRIC ACID.' BY EDWARD HART Received January 7, rags.
I
N a previous paper I described a tube condenser for use, among other things, in the condensation of nitric acid. Further experience with this condenser has enabled us to obtain still better results. W e can now obtain a distillate very low in nitrogen peroxide. T h e specific gravities of the distillate are about as follows : 84 pounds. 1st distillate.. ................ s p . gr., 1.j27 83 2nd .................. 1.526 43 3rd .................. 1.523 '
"
82 ?;
"
"
'I
"
1512
',
"
1.504
"
1.693
7; 74
'. 'I
''
1.4s;
74
',
'
1.435
47 47 57
I )
I474
'.
.'
1.48
"
1.300
785
9th 10th 11th
'*
''
'
.................. .................
''
I'
T h e amount of fuel necessary is surprisingly low if proper care is taken. For the distillation of 1,000 pounds nitrate, we use regularly but 150 pounds of pea anthracite coal, working day turn only; this is, no doubt, largely due to the short time within which the distillation has been brought by the use of this condenser, the distillation proper occupying but six hours, aiid the entire time, including charging and discharging, eight hours. During the night the retort and masonry, of course, cool off. I have no doubt that by running two shifts--day and night-the coal necessary could be brought within 125 pounds for the same weight of nitrate. Source (4 the Nitroge?i Peroxia'c Produced. -The contrast in color between nitric acid produced on the small scale in glass, and that made on the large scale in iron retorts, is very noticeable and I have been at some pains to look into the cause, since this formation often represents a dead loss to the manufacturer. I shall later on call attention to a period in the ordinary distillation during which, with no increase in the firing, the acid 1 R e a d a t t h e Boston Meeting, Dec. 27, 1%.
SOME POINTS ON THE DISTILLATION OF NITRIC ACID.
581
conies over very rapidly. It has often been noticed that during this stage, the acid is unusually white. I attribute this to the rapidity with which the gas passes from the retort, and consequent decrease in decomposition caused by the radiated heat. The same thing is noticed by distilling in glass. Certainly, therefore, part of the nitrogen peroxide is due to too long heating of the vapor, and the importance of an efficient condenser and a rapid distillation is evident. The effect of concentration of the vitriol on the color is very evident. T h e ease with which concentrated nitric acid is decomposed is well-known and, as might be expected, the strong acid made from distilled vitriol and dry nitrate shows much stronger color than that made from the less concentrated materials. I n glass, heating over a Bunsen, such acid may be obtained without difficulty of only a pale straw color, but in the ordinary iron retort the crude aqua fortis will frequently contain as niuch as three per cent. nitrgen peroxide. I t is the common opinion among acid makers that part of this color, perhaps a large part, is due to action of the acid on the iron. In most cases this is no doubt true, as the retort, as ordinarily set, is but imperfectly heated at the ends. I n the retorts which I have been using, however, the retorts are entire@ surrounded with the fire gases. It is quite possible, however, that even here the iron is notably attacked. Part of the color, no doubt, arises from impurity of the materials-chlorine, organic I suspect that material, aiid iron in solution principally-but this is responsible for only a part of the trouble. A gentleman who has for years carried on the distillation of nitric acid on the large scale, recently informed me that he had distilled fused nitrate and white vitriol in iron with no perceptible diminution of the color in the product. As stated in the books, the only reactions occurring are NaNO,+ H,SO, = NaHSO, HNO,, or 2NaNO,+ H,SO, = Na,SO,+ 2HN0,. I n practice only the first reaction is usually employed, especially where, as in acid for mixed acids, to be used for nitroglycerol, the product must be a s concentrated as possible. I n this
+
582
E D W - I R D HAR’P.
S O M E POINTS O N
connection, however, one point I think should be iioted that seeiiis to have escaped attention, that is, that with weak vitricl the water is largely retained b y the cake until the last stage of the operation, ant1 greatly assists tlie decoiiiposition giving a fair acid arid :i cake which is pi-actically infusible. If, however, strong vitriol is used, the decoiiiposition is iiicoiiiplete and the acid exceedingly red. 7 % F~oflli~zg.-This ~ matter of frothing is one that frequently gives great trouble to the nitric acid distiller, especially where weak acid and wet nitrate are used. T h e frothing begins in such cases after about seven-elevenths of tlir acid has distilled over. T h i s is easily demonstrated by conducting a distillation in glass with acid of 1.80 sp. g r . , or less. T h e trouble becomes then plainly apparent, and is evidently due to the decomposition of the NaHSO, a t first produced into Sa,S,O, and water: H,O. T h a t this is tlie reason may easily 2 X a H S 0 , = ?;a,S,O, be demonstrated by heating in another similar retort a mixture of dry sodium sulphate and sulphuric acid. \Ve then have NaHSO, formed, and 011 continuing the heat tlie same frothing is noticed, although the distillate is, of course, entirely free from nitric acid. Frothing over is prevented by giving sufficient capacity to the retort, and b y care and skill in firing. Keither alone is sufficient to prevent it. Kate ofDistillatzbn.--One of tlie most remarkable things in the distillation, especially noticeable in glass and with pure dry materials, is the variation in the rate of distillation and the almost explosive evolution of acid, which takes place, for a short period, after about three-tenths of the acid has distilled over. For exaiiiple: I n distilling in glass zoo grariis sodium nitrate arid 2 3 j grams distilled sulphuric acid, the proportions required by the equation N a N 0 , f H,SO, = N a H S 0 , f HNO,, the followiiig results were obtained. I t should be understood that the Bunsen, over which the operation was conducted, was allowed to reniaiii untouched, except where noted, aiid that the apparatus was shielded from air currents. T h e thermometer bulb was shielded from radiation by placing it within a porcelaiii crucible iii the retort.
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T H E DISTILLATION OF NITRIC ACID. Time. :46:40 2:43:zj i
Time interval.
.....
T e m p e r a - T e m p e r a - Acid disture. ture interval. tilled.
Distillation b e g u n .
I
:43 1:j7
110.
25
5
: 5 0 : 20
2 : 10
2:55:
2
3' 4' 7" 49 5'
10
2 : 5 2 : 30
113' 117' I 24'
2
15
2:59:00 3:02:0n
3 : 02 : 55 j : 0; : 30 3:04:w 3 : 04 : 45 3:17:40
:45
3 : 50 3 : 00 0 : 55 0 : 35
128'
'33'
00.
126'
10
50
135.
9O
55
I3O 9'
60 65
0
: 45
148'
3 : 45 : 2 0
.....
3:52.00
.....
30
125'
I 2 : 55
5 :40
25
125'
: 30
3 : 23 : 30 3 : 38 : 30
15 20
35 40 45
--8'
125'
0
157-
-5'
152-
O'
3 : 58 : 30 4:03:w 4 : "4 : 45 4:06:00 4 : os : 15
4 : I2 : 20 4:16:00
..... .... ..... ..... ..... ..... .....
158' 170'
178'
180' 194* 2009
Remarks.
...
108'
1
Acid not running, c l ar flsioii, lanip turnes u p . 1275 R' 80 L a m p turned still h i g h e r . '4O 85 6" 90
2209
200
246'
26
583
2o
96
Froth rises. Froth very h i g h . Froth s i n k i n g . No froth t i 0 froth. Mushy m a s s f u s i n g to c l e a r liquid b e l o w . Half fused. Three-fourths fused. Piece o f c a k e dropped into fused m a s s , lowe r i n g temperature.
1
I
No f r o t h . No froth.
S l i g h t froth. Half-inch froth. Retort full of froth duri n g t h i s interval. Froth g o n e , l a m p turnedout.
1
T h e drop of the temperature at 1 3 3is, ~ I think, unmistakable, and reminds one of the rise of temperature produced in the crystallization of a supersaturated solution. There we have the change from the fluid to the solid condition-here from the solid to the fluid. This explosive evolution is noticeable also in distilling in iron on the large scale and, perhaps, explains in part the difficulty nitric acid makers have hitherto had in properly condensing their product. By proper firing, and with a properly set retort, this difficulty is lessened. T o decompose strong nitric acid by heat or by its action on iron, and then to drive off the nitrogen peroxide with great pains and loss, is evidently a clumsy and probably unnecessary operation. I shall, therefore, make a determined effort to so arrange the retort that this will be in future unnecessary. There would seem to be no insuperable obstacle in the way of so conducting the distillatioii that even the first distillate would be of a pale straw color, like that made in glass, atid quite fit for the manufacture of dynamite and other nitro compounds with no purification whatever.
5 84
N E W HOOKS.
T h e use of nitro compounds has, of late years, beconie so large that a rational niethotl of conducting the process of nitric acid distillation is imperatively called for. I3erthelot has shon.11that sti-ong nitric acid is coniplete1)- decorriposed at about 360" into nitroger1 peroxide, ox!-gcn, and ivater. I t is certaiii that \\.it11 t h r retorts entirely surrounded 1)). fire gases the temperature of the upper part of the retort exceeds IOO'. It is not surprising, therefore. that the first distillate should show a dark red coloi.. .4 recent distillatioii i n glass, with pieces of cast iron iiiiniersect i i i the tuisture of acid arid nitrate. gave no additional color to the first clistillate.
NEW BOOKS. nS I:. I'I.:CKl;,L MGI,I.ICK, I'H.D. 1.011d o n : Peter Moller. N e w York : \\*rn. IT. Schieffelin SL Co. Printed for private distribution.
C O I ) - L I V E K 011. A S D C H E M I S T K S .
T h i s book is reall) two books in one. T h e first part treats of cod-liver oil, the methods of catching the fish, the preparation of the oil, and an account of its constituents. W e learn that codliver oil was originally made froin fresh cod-livers by the steam process, by Peter Moller, i l l I8j3. T h e oil so prepared \vas a great improvemerit over the older product prepared by the putrefaction of the livers. I t still, however, caused disagreeable aftereffects when exhibited, and to reniedy this ail investigation was undertaken by P. b l . Hyerdahl, presumably in the employ of Peter Moller. Mr. Hyerdahl finds that the disagreeable aftereffects are caused by the presence of hydroxy acids in the oil, and that these may be excluded by reiidering the livers iii a n atmosphere of carbon dioxide. T h i s process is now carried out by Peter hloller, therefore buy your cod-liver oil of this firm. T h e deduction is not so stated ir; the book, which is well written and gives a very readable account of the subject, but the advertising purpose is obvious. I t is a pity that Mr. Hyerdahl's work was not made known through the regular channels-the Beyichtc for example. Chemists will be apt to look with suspicion upon statements so obviously interested.
