1214
IiYD UST R I A L AND EXGINEERIKG CHEMISTRY
Colored solutions were titrated electrometrically. Some titrations were made with alcoholic potassium hydroxide standardized against pure stearic acid. Water solutions were referred to sodium carbonate as ultimate standard. All solutions were cross-checked to eliminate possible errors. I n all cases duplicate acid numbers checked satisfactorily within the limits of experimental error. The average results are shown in Table 11. This shows that boiling the acetone extract with water increases the acid number. It seemed as if a similar effect ought to be noted on very long heating with water on the steam bath. On testing this, the results in Table I11 were obtained. of Long Heating w i t h Water ACID&-UMBER Water extraction of acetone extract SS-1 53 Extracted 12 hours on boiling water bath 53 Residue from C boiled with water 6 hours 97 Table 111-Effect
A
C
D
Discussion
The value A in Table I1 for SS-1 should agree with -11in Table I, as both are supposed to be measures of water-soluble acids only. Value B (Table 11,SS-1) agrees with X (Table I) as it should, because both measure acetone-soluble acids only. I n the case of SS-2 in Table 11, the value A(42) should equal the values (489, 399) obtained by direct water extraction if nothing is happening except simple extraction. To determine whether a similar effect could be noted in extracting an acetone extract with water, several acetone extracts were boiled with water as indicated. I n every case the acid numbers increase with time of boiling. However. as Table I11 shows,
1’01. 20, KO. 11
the water must be near the boiling point, for no effect on the acidity was noted by heating a fresh acetone extract with water for 12 hours on a water bath, but the residue from this water extraction gave an increase in acid number of 97 when boiled with water. Conclusion
From the results obtained it is concluded that the boiling water hydrolyzes some of the esters in the acetone extract. I n the case of direct extraction of the rubber with water. hydrolysis of esters must take place in the rubber, forming Tvater-soluble acids; or else, although the esters are practically insoluble in the water, it extracts a little ester each time the extraction thimble empties (Bailey-Walker apparatus), carrying the ester down to be hydrolyzed in the boiling water below. Temperature and time of heating play a prominent part. The temperature must be close to the boiling point and the acidity increases progressively with time of heating. The fact that temperature is so important in producing this effect accounts for the erratic values obtained by direct water extraction. On the electric hot plates used water did not always boil steadily, and that contained in the thimble might vary considerably in temperature, much of the time not being hot enough to hydrolyze or extract any ester. Therefore, to avoid any difficulty in the determination of water-soluble acids in rubber, extract first with acetone. then digest this extract with water on a boiling water bath until no increase in acidity of the water extract is obtained. This is a part of the procedure developed a t the Netherlands Government Institute by T7an Rossem and Dekker.
Heating Value of Coal in Nickel-Lined Bombs’ A. E. Stoppel and E. P. Harding UNIVERSXTY
I
OF
MINNBSOTA, hfINNEAPOLIS,
T IS generally known that the nitric and sulfuric acids formed during the combustion of coal in an oxygenbomb calorimeter having a nickel !ining do not appear entirely as such in the bomb washings, but partially or completely attack the lining and appear either wholly or in part as nickel nitrate and nickel sulfate a t the completion of the determination. Thus, when the washings are titrated, too little acid is found, and the thermal correction for acidity is likewise too low when the usual methods for making the correction are applied as in the case of a non-corrosive bomb lining. Furthermore, unless some correction is made for the corrosive effect of the acids upon the lining, another source of error is introduced. Olin and Wilkinsz showed that the sum of these two errors, if neglected, may lead to heating values which are over 2 per cent too high for coals containing about 4 per cent of sulfur. Later, a study of the corrosion on monel-metal bombs was made by Geniesse and Soop,3 who developed a correction to be applied to the observed heating value, based on the titration of the bomb washings for free acid, and the total sulfur in the coal. They showed that by making such a correction it was possible to reduce the error to less than 0.4 per cent in the case of monel-metal bombs, and suggested that a similar correction would be applicable for nickel-lined bombs. 1 2
3
Received April 12, 1928. Ckem. Mer. Eng., 26, 694 (1922) IND. E m . CHEM, 17, 1197 (1926).
MI”.
Proposed Method for Determining Corrosion in KickelLined Bombs
The writers have found it possible to determine the amount of corrosion in nickel-lined bombs with a sufficient accuracy for technical purposes by titrating the bomb washings with a standard sodium hydroxide solution, using two indicators, methyl red and phenolphthalein, both of which are available in any laboratory where the heating Talue of coal is determined by means of an oxygen bomb calorimeter. The bomb washings are boiled 2 or 3 minutes to remove carbon dioxide, after which methyl red indicator is added and the solution is titrated with 0.1 ATsodium hydroxide solution. This measures the total amount of free acid present. About 1 cc. of phenolphthalein is then added and the titration continued until the red color of the phenolphthalein shows through the yellow of the methyl red. This end point, however, disappears on boiling the solution. More alkali is added until the indicator is again colored, after which the solution is again boiled. The end point to be taken is the one a t which a rather strong red color is permanent after 2 or 3 minutes of brisk boiling. This may best be seen by allowing the greenish precipitate of nickel hydroxide to settle and observing the supernatant liquid. I n the case of large quantities of nickel sulfate or nitrate this may require five or six subsequent additions of alkali and boilings before a permanent end point is reached. After a little practice the titration can be made fairly rapidly. The reactions for
I S D U S T R I A L A S D E,VGINEERING CHEMIXTRY
Sovember, 1928
1215
value of 3949 * 3,s calories as an average of fire determinations made in an illium bomb calorimeter. This work was divided into two parts. I n runs 1 to 6 of Table I11 combustion took place in an oxygen atmosphere NiS04 2h’aOH = Ni(OH)* NazSOa 2NaN03 Ni(N03)2 + 2NaOH = Ni(OH)z containing only a small quantity of nitrogen, so only small The accuracy of this method for determining the amount amounts of nickel nitrate were formed. Before each deterof soluble nickel is shown by the following determinations mination, most of the atmospheric nitrogen present within made on a solutiou of recrystallized nickel sulfate. The the bomb when it was closed was remored by filling the bomb colution was found to be neutral to methyl red, and its nickel with oxygen to about 10 atmospheres pressure, and then content was determined gravimetrically by the dimethyl- slowly releasing the pressure to atmospheric. This process glyoxime methode4 Twenty-five cubic centimeter portions was repeated several times. Finally the bomb was filled of thic solution gaye 0.02681, 0.02672, 0.02695, and 0.02681 with 26 atmosphkres of oxygen pressure, and the deterpram of nickel, respectively, with an areracpe of 0.02682 mination was comoleted. I n runs 7 to 13 the bomb was a &-amnickel. first filled to 4 or 5^ atmospheres Dressure with nitrogen gas. iollowed by oxygen to a Table I shows that the total pressure of 26 to 28 att i t r a t i o n method gives A rapid method has been developed for determining mospheres, before making slightly low results with the amount of nickel dissolved in a nickel-lined bomb the combustion. I n t h i s solutions of nickel sulfate. by action of the nitric and sulfuric acids resulting from case much larger quantities The experiments reported the combustion. This method involves merely a of nickel nitrate were obin Table I1 were made on titration of the bomb washings for free acid in the tained, and from this difactual coal-combustion deusual way by means of standard alkali and methyl red ference was calculated the terminations in which the indicator, followed by a continuation of the titraheat formed by the action of bomb washings, after titration in hot solution with the same standard alkali the nitric acid on the lining. tion by the above method, solution to a second end point using phenolphthalein That complete combustion were acidified with hydroas indicator. The heat of reaction and solution of is obtained under this preschloric acid to dissolve the nitric acid on the bomb lining has been determined, sure of nitrogen has been precipitated nickel hydroxand directions are given for making a correction for shown by Kohout.5 After ide, the insoluble coal ash corrosion in determining the water equivalent. each run the bomb linings filtered off, and the nickel A method is proposed for making a correction for were immediately washed content of each solution decorrosion in determining the heating value of coal, out, and the washings tit ermined gravimetrically by which involves merely a titration of the bomb washtrated for free acid and for t h e glyoxime method. ings for free acid, and for combined acid, and a knowlc o m b i n e d acid as nickel Coals varying in sulfur conedge of the total percentage of sulfur in the coal. nitrate. The calorimetric tent from 0.5 t o 5.5 per cent Heating values obtained by this method agree within determinations were made n-ere used, t h e a m o u n t 0.3 per cent of those determined on the same coal by in all cases as recommended burned varying b e t we e n means of a non-corrosive illium bomb for coals conin the American Society for 0 . i 5 and 1.25 grams. taining up to 9 per cent sulfur. T e s t i n g Materials StandS o t quite PO good agreeards for 1927. Exactly 2 ment between the volumetgrams of sugar were burned ric slid gravimetric methn_ d_s_ was obtained here as in the case of the oure solution of in all the determinations. The thermometer used was cernickel sulfate. This may be due to minor impurities in the tified by the Bureau of Standards. nickel lining itself or, more probably, to the character of the ash in the coal burned, part of which is usually found in the Table 11-Comparison of Titration and Glyoxime Methods for Determining Bomb Corrosion bomb washings, and which may slightly influence the titration and thus cause the discrepancy noted. However, a maximum 0 . 1 A’ SODIUM HYDROXIDE NICKEL difference of about 2 mg. of nickel was found. as will be shown Methyl PhenolTitration Glyoxime Difference red phthalein later in this paper, to amount to about 3 calories, which is well within the limit of accuracy of coal calorimetry as a whole. cc. Cc. Gram Gram Gram S o claim is made that the method is quantitatively exact, 0.0 27.4 O.OS03 0.0001 O.OS04 0.0020 0.0963 3.1 33.5 0.0983 but it is sufficiently >o for technical purposes. 2.1 34.5 0.0008 0.1004 0.1012
the phenolphthalein end point are as follows in the case of nickel sulfate and nitrate. both of which are usually present in the bomb washings when coal is the substance burned:
++
+
-
I
~~
I
Table I-Titration Xi
0.1 N
TAKEKNaOH
Gram 0.0107 0.0107 0.0214 0.0268 ( I nm8
Ni
DIFF.
FOUND Ni
Gram Gram 0.01OS 0,0001 0.0107 0,0000 0.0212 -0,0002 0,0268 0,0000 9.10 0.0267 -0.oo01 Cc.
3.68 3.66 7.21 9.12
I 1
Ni 0.1 N Ni DIFF. TAKENNaOH FOVND Xi
Gram Cc. Gram 0.0322 10.88 0.0319 0.0536 18.10 0.0531 0.0804 27.25 0.0800 0,0804 27.15 0,0797 0.1072 36.40 0,1068
Gram -0.0003 -0.0005 -0.0004 -0,0007 -0.oo04
Determination of Water Equivalent To determine the amount of heat liberated by the action of nitric acid on the bomb lining to form nickel nitrate, a number of combustions mere made on a sulfur-free substance. For this purpose cane sugar was chosen, a sample of which was found to be uniform in composition and to have a heating 4
0.1 0.1 0.0 0.0 0.0 0.3 0.3 1.2 0.2 0.5 0.2 0.3
of Nickel Sulfate Solution
Treadwell-Hall “.inalytical Chemistry,” 1701 IT, p 129 (1919)
9.6 9.65 8.1 14.1 12.3 21.5 20.8 22.9 23.0 20.6 14.7 14.6
0.0282 0.0283 0.0238 0.0414 0.0361 0,0630 0.0610 0.0672 0.0676 0.0604 0.0431 0.0428
0,0277 0.0286 0.0242 0.0412 0.0364 0.0609 0.0608 0.0672 0.0670 0.0598 0.0435 0.0441
0.0005 -0.0003 0.0004 0,0002 0,0003 0.0021 0.0002 0.0000 0.0005 0.0006 - 0.0004 -0.0013
-
The results in Table I11 are reported in terms of water equivalents, since the heat of combustion could not be determined in a nickel-lined bomb without a knowledge of the amount of heat liberated when nitric acid acts on the lining. According to Thomsen6the heat of formation and solution for the reaction Ni-O-NzOs-ilq is 83,420 calories, u-hile the 5 6
IND. ENG.CHEM.,19, 1065 (1927). “Thermochemistry,” Longmans, Green and Co , 1908
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1216
Table 111-Combustion TITRATION 0.1N NaOH
Free
HGATO F COMBUSTION
acid (1)
Combined acid (2)
2 Grams sugar
cc.
cc.
Cal.
(3)
Iron fuse wire (4)
TEMP.
HEATDUE TO FORMATION OF Ni(N01)z
(6)
c.
Cal. A-IN
of Cane Suaar
2X5.62 (5)
Vol. 20, s o . 11
Cal.
2X4.50 (7)
Cal.
2X2.73 (8)
WATEREQUIVALENT 3+4+6 5 (9)
3+4+i 5
3+4+8 5
(10)
(11)
Cal.
ABSENCE O F A N APPRECIABLE QUANTITY O F NITROGEN
B-IN
PRESENCE OF NITROGEN
0.0 0.0 0.0 0.0 0.0 0.0 0.0
accepted value for the reaction Nz-05-Aq7 is 1035 calories per gram of nitrogen, or 28,980 calories for the production of 2 molecules of dilute nitric acid. The total heat of reaction and solution for Ni-Nz-Os-Aq is therefore 112,400 calories, or, expressed on the basis of 1 cc. of 0.1 N nickel nitrate solution, i t would amount to 5.62 calories. The figure for the reaction Ni-0 to form NiO is 57,900 calories. The heat of formation and solution for NiO-NrOs-Aq is therefore 54,500 calories, or 2.73 calories per cubic centimeter of 0.1 N nickel nitrate solution. The water equivalent in column (9) of Table I11 has been calculated with the assumption that the bomb lining has a surface of metallic nickel; in column (11) the surface is considered to consist entirely of nickel oxide; while in column (10) a surface of mixed metal and oxide is assumed. By comparing these three columns with reference to parts A and B, it will be seen that column (10) gives the best agreement for the value of the water equivalent. In column (9) the average value of series B is 0.17 per cent higher than that of series A, while in column (11) it is 0.25 per cent lower. It is therefore assumed that the surface of the lining which is subject to corrosion consists of a mixture of metallic nickel and nickel oxide, or that the metal is covered with a thin film of oxide. It is further assumed that the proportion of metal to oxide on the surface is fairly constant, and that during corrosion the acid acts on both in the approximate proportion of 25 per cent oxide to 75 per cent metal. An arbitrary factor of 4.50 calories for each cubic centimeter 0.1 N nickel nitrate formed is therefore proposed as the proper correction to be applied for the corrosion. Further evidence that this is the proper factor will be shown later in determining the heat of combustion of coal, where it will be seen that the use of this value gives results for the heating value of coal in fairly good agreement with those determined in a bomb having a non-corrosive lining. The lining used in this work had been in use for a number of years. It had the typical tarnished or corroded appearance, indicating the presence of a t least a film of oxide. It is believed that it is fairly representative of any lining that has been in use for some time. Although the corrosion is ordinarily small in making a determination of the water equivalent, the error, if neglected, will be much greater than the other experimental errors involved in making the observations. The writers have found that under normal conditions of determining the water equivalent, where the bomb contains the nitrogen of the 7
Bur. Mines, Tech. P a p n 8 (1926).
air present before filling with oxygen, about 6 cc. of 0.1 LV nickel nitrate are formed during the combustion, and failure to correct for this will introduce an error in the water equivalent of the instrument amounting to about 0.4 per cent. Correction for Bomb-Lining Corrosion in Combustion of Coal
I n determining the heating value of coal by means of an oxygen-bomb calorimeter, a thermal correction is ordinarily made for the amount of nitrogen oxidized to nitric acid under these conditions, and for the oxidation of the sulfur in the coal from the dioxide to the trioxide with subsequent solution to form dilute sulfuric acid. I n the case of nickel-lined bombs an additional correction must be made for the quantity of these acids which react on the lining with the resultant formation of dilute solutions of nickel sulfate and nitrate. Thornsen’s figure for the heat of formation and solution of Ni-O-SOTAq is 86,950 calories. The commonly accepted figure for SOz-0-Aq is 2200 calories per gram of sulfur, or 70,400 calories for the molecular heat. The total heat of formation and solution for Ni-Oz-SOrAq is therefore 157,350 calories, or 7.868 calories per cubic centimeter of 0.1 N nickel sulfate solution. As previously shown, the heat of formation and solution for the reaction Ni-Nz-OB-Aq is 5.62 calories per cubic centimeter of 0.1 N nickel nitrate solution. The difference between the last two figures, divided by 0.0016,the value of 1 cc. of 0.1 N sodium hydroxide solution in grams of sulfur, equals 1405 calories per gram of sulfur, or 14 calories per centigram of sulfur. This calculation is based on the assumption that the bomb lining is metallic nickel. It has been shown, however, that t h surface consists of a mixture of metal and oxide. Such being the case, both factors-i. e., 5.62 calories for P cc. of 0.1 N nickel nitrate and 7.868 calories for 1 cc. of 0.1 X nickel sulfate-would be lowered by a constant amount, and the additional correction to be added would still be 14 calories per centigram of sulfur. I n making the correction for combined acid in the bomb washings as measured by the phenolphthalein titration, it is only necessary t o multiply the cubic centimeters of 0.1 N alkali required for this titration by 4.50 calories, assuming only nickel nitrate to be present, and then add 14 calories for each 0.01 gram of sulfur present as nickel sulfate. If free acid is found in the bomb washings as measured by the titration using methyl red indicator, it is corrected for in the usual manner as in the case of non-corrosive bombs by multiplying $he cubic centimeters of 0.1 N+akaliqequired
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November, 1928
by 1.45 calories to correct for the nitric acid, and then adding 13 calories for each centigram of sulfur present as free sulfuric acid. However, where both free and combined acids are found in the bomb washings, the free acid probably contains both nitric and sulfuric acids, and likewise the combined acid both nickel nitrate and sulfate, and there is no simple method to determine the distribution of each acid in either the free or combined state. However, the difference between 13 and 14 calories is small as applied to a calorimetric correction, so it is probable that either value could be taken for the additional correction to be made on the total sulfur in the coal. Since, however, the combined acid predominates in every case when the bomb washings are titrated, it is evident that 14 calories is the more correct figure. Table IV-Heating OBSn. HEATOF
RUN
SULFUR
CoxBUS-
Value of Coal in Illium Bomb 'ORRECTIOB FOR
TITER 0 . 1N
NaOH
H E ~ VALUE
ACID
Hxoa
s
3 x 1 45 (4)
1x13
CUI. 6 6 6
%
Cal.
cc.
Cul
0.45
8365 8355 8358
13.7 13.9 14.1
20 20 20
17 18 19
0.57
8100 8104 8104
13.7 14.6 15.0
20 21 22
7
20
1.27
21 29
7489 7498 7507
16 5 17.0 17.3
24 25 25
17 17 17
23 24 25
1.43
7752 2740 ,764
16.8 19.4 18.1
24 28 26
19 19 19
26 27 28
2.37
6802 6814 6811
21.0 21.0 21.6
30 30 31
31 31 31
29 30 31
2.92
6i71 6783 67S2
24.2 23.6 24.1
35 34 35
38 38 38
32 33 34
3.58
6520 6505 6509
26.9 27.3 26.4
39 40 38
46 46
35 36 37
5.07
6458 6467 6454
36.0 37.2 37.0
52 54 54
66 66 66
8.82
5069 5077 5065 5053
60.3 64.5 60.0 59.4
87 94
115
87
86
2-(4
(5)
14 15 16
+ 5)
(6)
7
7
iii 115
T
(CUR.)
1
CUI. 8339 8329 8332 Av. 8333 8073 8076 8075 Av. 8075 7448 7456 7465 Av. 7456 7709 7693 7719 Av. 7707 6741 6753 6749 Av. 6748 6698 6711 6709 Av. 6706 6435 6419 6425 AY. 6426 6340 6347 6334 Av. 6340 4867 4865 4863 4852 Av. 4863
on a series of coals ranging in sulfur content from 0.45 to 8.82 per cent in an illium bomb which is non-corrosive to the acids formed during the combustion. The results were compared with those obtained by a similar series of determinations on the same coals in a nickel-lined bomb. making the proposed correction for corrosion. Both bomb> had about the same volume, approximately 400 cc. Exactly 1-gram samples of coal were burned in all cases with an oxygen pressure of 25 atmospheres. The water equivalent.. of both instruments were determined by combustion of Bureau of Standards benzoic acid, with results agreeing to *O.l per cent, making a correction for corrosion in the nickel-lined bomb. The same thermometer was used with both calorimeters and was certified by the Bureau of Standards. The sulfur in each coal was determined by Eschka's method. Table IV gives the results obtained for the heat of coni~ ~ ~ in an illium bomb with the corresponding correcbustion tions for acidity. Table V gives the results on the same coal2 with the nickel-lined bomb, using the proposed method of correcting for corrosion. Complete data have been given to show the relative agreement of duplicate runs on the same calorimeter, and the average agreement of both on the same coals. The results show that duplicate determinations check to about the same degree of accuracy with both instruments. and that the average results on the same coal as determined by both check to within 0.3 per cent, which is the maximum limit adopted by the American Society for Testing Material.. Possible Side Reactions during Corrosion
When hot nitric acid acts on metallic nickel, it undoubtedly acts as an oxidizing acid, and a part of the nitrogen must be reduced to a lower state of oxidation, such as oxides of nitrogen, free nitrogen gas, or possibly even to ammonia, in which caGe it would appear in the bomb washings as ammonium nitrate. Experimentally, a smaller quantity of total acid (free and combined) was always found in the washings of the nickel-lined bomb than in the illium bomb, whereas theoretically it should have been about the same, since both bombs had practically the same volume and determination. were made with the same oxygen pressure. This was found to be true in the combustion of sulfur-free substances as well as in the case of coal. Only traces of ammonia could be detected by nesslerization of the bomb washings resulting from the combustion of cane sugar. It is more probable that the reaction 5Ni
Method of Making Corrections
After each run the bomb is immediately washed out to prevent further corrosion, and the washings are boiled to remove carbon dioxide. Methyl red indicator is added and the free acid is titrated with 0.1 N sodium hydroxide solution. Each cubic centimeter of titration is multiplied by 1.45 calories to correct for the free acid. One cubic centimeter of phenolphthalein indicator is added, and the titration is continued until a second end point is reached which is permanent after a couple of minutes' boiling. Details of this second end point have already been given in the first part of this paper. The number of cubic centimeters of alkali required for the second titration is multiplied by 4.50 calories to correct for the combined acid. To the sum of these two values are added 14 calories for each centigram of sulfur in the coal burned. Comparison of Results Obtained in Illium and NickelLined Bombs
I n order to test the accuracy of this method of making the correction for corrosion, several determinations were made
121i
+ l2HNOi = 5Ni (NO& + Nz +6H20
takes place, since by this assumption only five-sixths of the acid formed during the combustion would appear in thr titration of nickel nitrate, and such an assumption would very nearly explain the differences found in the titrations ot the washings from the two bombs when a sulfur-free substance was burned. It will be noted, however, that if nitrogen is liberated it will be present in its original state in the bomb, and no further correction need be made. Likewise, when hot sulfuric acid reacts on metallic nickel it will probably also have an oxidizing effect, and become reduced to some lower state of oxidation. No soluble sulfites could be detected, however, in the washings from thc combustion of a 5 per cent sulfur coal, one drop of 0.1 A iodine solution giving a strong blue color when added to the washings in presence of starch emulsion. Occasionally. on opening the bomb after a combustion, traces of a black deposit are noticed on the lining. This was especially marked in the case of the 8.82 per cent sulfur coal, which gave R dense, adherent, black deposit on the lining. This deposit was soluble in dilute hydrochloric acid, hydrogen sulfide being given off in sufficient quantity to give a distinct odor
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1218
Table V-Heating RUK
SIiLFUR (1)
OBSD. HEATO F COMBUSTION (2,
Vol. 20, No. 11
Value of Coal in Nickel-Lined Bomb
TITER 0 . 1 N NaOH Free acid
Combined acid
(3)
CORRECTION
FOR
ACID
S
(4)
3X1.45 (51
Ni(N03Jz 4X4.50 (6)
1x14 (7)
Cal.
Cal.
Cal.
Cal.
*.
52 55 54
6 6 6
*.
56 53 56
8 8 8
8342 8335 8327 8335 8054 8058 8059 8057 7458 7459 7453 7457 7693 7694 7682 7690 6736 6748 6726 6737 6703 6713 6692 6703 6428 6424 6424 6425 6334 6331 6340 6335 4857 4861 4867 4846 4858
%
Cal.
cc.
cc.
42 43 44
0.45
8400 8396 8387
0.2 0.2
0.0
11.6 12.2 11.9
45 46 47
0.57
8118 8119 8123
0.1 0.1 0.0
12.5 11.7 12.5
48 49 50
1.27
7542 7543 7534
0.2 0.3 0.3
14.7 14.6 14.1
.... ..
66 66 63
18 18 18
51 52 53
1.43
7781 7780 7771
0.0 0.0 0.1
15.1 14.7 15.4
.. .. ..
68 66 69
20 20 20
54 55 56
2.37
6853 6862 6838
0.2 0.1 0.4
18.6 18.1 17.3
..
*. 1
84 81 7s
33 33 33
57
2.92
6843 6849 6834
1.1 1.0
1.1
21.6 20.6 22.2
2 2 1
97 93 100
41 41 41
6582 6375 6572
0.9 1.5 2.4
23.2 22.3 21.4
1 2 3
104 96
49 49 49
6537 6535 6633
6.2 6.2 6.7
27.4 27.5 24.9
9 9
10
123 124 112
71 71 71
17.1 23.7 20.6 20.4
36.3 30.7 34.3 33.6
25 34 30 30
163 138 154 151
123 123 123 123
5s 59
60 61 62
3.50
63 64 65
5.07
66 67 68 69
and to turn lead acetate paper brown on prolonged exposure. With this coal abnormally low results were always obtained on the following run unless the lining had been previously cleaned. It is also conceivable that free hydrogen might be liberated according to the reaction Ni
HEATINGVALUE Av. DIFF. (COR.) FROM ILLIUM 2-(5+6+7) BOMB (8) (9)
HNOs
+ H804 = NiS04 + Hz
especially if the acid is condensed after the bomb has reached room temperature. Subjection of the gas in the bomb, after combustion of a sample of 5 per cent sulfur coal, to the usual absorption methods of gas analysis, followed by an explosion indicated the presence of only traces of hydrogen. It is possible that in the burning of a high-sulfur coal, with the resultant production of a considerable amount of acid, any free acid present in the bomb when the temperature is a t equilibrium may continue to act slowly on the lining, liberating a small quantity of heat, thus affecting to a small extent the final radiation drop and likewise the final radiation correction. In the following determination on a 5.07 per cent sulfur coal the pressure was released 4 minutes after firing; the bomb was then opened and the lining washing completed 6 minutes after firing, thus preventing further corrosion due to free acid. The titration of the washings consumed 9.5 cc. of 0.1 N alkali for free acid, and 23.5 cc. for combined acid. I n the normal case, where temperature readings must be taken for at least 10 minutes after firing in order to calculate the final radiation correction, the bomb cannot be opened and the lining rinsed until about 12 minutes after firing. Comparison of the above titration with those of the normal, as illustrated by runs 63 to 65 of Table V, will show that about 3 cc. more free acid were present in the bomb 6 minutes after firing than there were 12 minutes after firing. The proposed factor of 4.50 calories for the heat of formation and solution of l cc. of 0.1 N nickel nitrate solution may therefore be a resultant of the assuniption of a mixed oxide
..* . .. ..
100
Av.
Av.
Av.
Av.
Av.
Av.
Av.
Av.
Av.
Cal.
- 18 +1
- 17 -11
-3
-1
-0
-5
and metallic lining and some of the side reactions noted above, which, although they may take place to only a small extent in comparison with the main reaction, would all tend to lower the figure of 5.62 calories, based on the assumption of a lining of metallic nickel and no side reactions. At least, the factor 4.50 calories, although largely arbitrary, when used in the practical case, gives results for the heating value of coal in fairly good agreement with those obtained by means of a bomb where no corrosion takes place, and this justifies its use.
Germany’s Chemical Exports Believed Back to Pre-War Volume Growth of Germany’s chemical exports the past several years has brought them to their former pre-war volume, according to the Chemical Division, Department of Commerce. Exports last year exceeded $300,000,000, an increase of about a quarter over the previous year and three-fifths over 1925. However, 1927 exports include reparations, which account for part of the gain. Germany’s efforts have been concentrated on greater foreign sales of fertilizers and industrial chemical products, which showed the largest increases in 1927. In these two main groups, accounting for more than half of the total chemical exports, improvements were made in such classes as methanol, acetone and formaldehyde, sodium chlorate, sodium sulfates, sodium silicate, cyanides, copper sulfate, iodine (mostly re-exports), magnesium sulfate, ethers of all kinds, and tartaric acid in the industrial chemical branch; and crude potash salts (18 to 42 per cent), potassium sulfate, sodium nitrate, ammonium phosphate and ammonium sulfate, calcium nitrate, and urea in the fertilizer group. Steady progress also has been made in exports of pyroxylin, which rose from 4100 tons in 1926 to 6200 in 1927. The bulk of Germany’s chemical trade is with Europe. In both 1925 and 1926 practically three-fifths of the total German chemical shipments went to Europe and one-fifth to Asia and Oceania, leaving only another fifth to be divided among all the Americas and Africa. The United States bought more chemicals than any other country in 1926, chiefly because of the size of its purchases of fertilizers.
