936
THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
water-soluble portions minus the nitrate and ammonia nitrogen would show the same relation to the amino and amide fractions as did the active insoluble portions of pure proteins. Table IV gives these figures, which are shown graphically in the figure, the values being plotted. in order of ascending values of the amino nitrogen. The similarity in trend is very apparent. It could not, of course, be expected that the results would agree since, for reasons already pointed out, the active insoluble portion includes only part of the amino nitrogen and a variable fraction of the acid amide nitrogen. Evidently the results with these materials do not show the same consistency as did those with pure proteins and the simpler compounds. I n 50 per cent of the cases, hydrolysis was apparently incomplete, assuming that all amino nitrogen liberated during acid digestion is capable of being ammonified in the permanganate digestion. This is shown by the fact that the ammonia produced in the process was not equal in amount to the total amino nitrogen. I n the other cases results analogous to those with proteins were obtained, i. e., apparently all of the amino and part of the amide nitrogen was ammonified. These results are, nevertheless, in harmony with the considerations stated above, it having been pointed out that the reaction is still incomplete a t the end of the digestion period in the permanganate method.
DISCUSSION AND SUMMARY In the light of the discussion in the earlier part of the paper, together with the experimental data, certain general statements regarding the availability of organic nitrogenous
Vol. 13, KO. 10
compounds seem justified. It is, of course, conceded that inorganic compounds of ammonia and nitric acid constitute a class of immediately available material. Assuming that the ammonifying, as distinguished from the aminojying or hydrolyzing, power of the alkaline permanganate solution is comparable to the action of soil agents, we may add to the nitrogen of the above members of the available class of compounds all amino nitrogen present in the form of aamino acids and a portion of that nitrogen present as acid amides. Then there is another class of compounds which we have called the potentially available class. It includes such substances as may be converted into members of the former class, and consists of a portion of the acid amides, the peptides, which can be hydrolyzed to amino acids, and primary and secondary amines. The peptides probably form the great bulk of this class so far as ordinary fertilizer maaterials are concerned. This class is the uncertain quantity in evaluating any material from the fertilizer standpoint. In some cases transformation into the available class is so easy and complete that there can be no practical distinction between the two. In other cases this process is so slow that the' other extreme, i. e., the unavailable class, is approached. Fundamentally, the problem of devising a method for the determination of the availability of organic nitrogen compounds is the invention of one which will properly estimate the rate of aminofication of the members of this class. Up to the present the permanganate methods have proved the most satisfactory. They are being studied further in the light of the work reported in this paper and the results will be published in the near future.
The Chemical Constitution of Soda and Sulfate Pulps from Coniferous Woods and Their Bleaching Qualities' By Sidney D. Wells MADISON,WISCONSIN U. S. DEPARTMENT OF AGRICULTURE, FORESTSERVICE,FOREST PRODUCTS LABORATORY,
In looking for a solution for the periodical shortage of raw materials for paper manufacturing, the investigator soon realizes the existence of the large and widespread supplies of wood too resinous for use in the sulfite process, and too resinous, dark colored, or hard for the manufacture of satisfactory mechanical pulp. Of all our standing timber only 3 per cent, existing in the Lake and Northeastern states, is available for use as a source of supply for the manufacture of over 70 per cent of our wood pulp production. In the same areas and in the southern states within a reasonable distance of the important publishing centers, occur stands of various species of pine, tamarack, and other coniferous woods amounting to 20 per cent of the total stand in the United States. They possess a very satisfactory fiber, but can be economically pulped only by alkaline processes, such as the soda or sulfate, by which the resinous matter is readily rendered soluble. Unfortunately, soda or sulfate pulps from coniferous woods are difficult to bleach t o a satisfactory degree of white, and only relatively small amounts are produced for special purposes. Even spruce, which is used in large quantities in the manufacture of bleached pulps by the sulfite process, yields a soda or sulfate pulp about as difficult to bleach as longleaf pine or tamarack. Many investigators have attributed this to the presence of impurities such as lignin, but the writer has long felt that it is due to coloring matter present in the wood or produced during digestion, which is very small in amount but of high tinctorial power. In fact, it has been 1 Presented
before the Section of Cellulose Chemistry at the Blst Meeting of the American Chemical Society, Rochester, N.Y.,April 26 to 29, 1921.
felt that sulfate pulps from the pines, spruces, and firs (even though cooked for strength and dark brown in color) more nearly approach cotton cellulose in chemical or physicd characteristics than well-cooked sulfite pulps from the same wood. Studies were therefore undertaken to ascertain the chemical characteristics of typical soda and sulfate pulps from white spruce which were cooked under carefully regulated and known conditions, and also of portions of the same pulps bleached to various degrees.
PREPARATION OF PULPS The pulps were cooked in the semicommercial tumbling digester in use a t the Forest Products Laboratory which has a capacity of 100 lbs. of dry pine chips, or a production of from 40 to 50 lbs. of bone-dry pulp per charge.' In Table I are presented the cooking conditions and yields of pulp obtained. The bleached pulps were prepared from the unbleached pulp described above by bleaching with definite amounts of bleaching powder solution a t 100" F. in glass vessels provided with mechanical stirrers. The bleaching operation in each case was continued until just a trace of active chlorine remained, as shown by starch iodide indicator. The pulps were then washed free from bleach residues, pressed, and allowed to dry by exposure to the air a t 70" F. They were then stored in airtight fruit jars until needed. The amounts IKress, Wells and Edwardes, "The Equipment and Operation of an Experimental Pulp and Paper Laboratory," Paper, a6, No. 13 (lglg), 11; Pulp Paper Mag. Can., 18, No. 23, 588.
T H E JOURNAL OF IhTDUSTRIAL A N D ENGINEERI-VG CHEMISTRY
Oct., 1921
Q37
TABLEI COOKIXGCONDITIONS--.---------Yield nf
COOS NO.
2 3 4 5
NaOH COOKING LIQUOR---Maximum Time Maximum In Volume per Concentration Chemicals per 100 Time at Steam Liquor 100 Lbs. NaOH NazS Lbs. Dry Chips Reaching Maximum Pressure a t End Dry Chip Grams Grams NaOH Na,S Pressure Pressure Lbs. per of Cook Gal. per Liter per Liter Lbs. Lbs. Hrs. Hrs. Sq. In. Lbs.
KIND Well-cooked soda pulp.. . 31.2 118.0 30.6 . 1.75 7.00 100 Ordinarily cooked soda pulp 26.8 98.5 . . 22.0 .. 4.00 3.50 100 Well-cooked sulfate pulp.. ., 32.6 85.4 22 .O 23.2 6.0 1.50 3.50 100 Ordinarily cooked sulfate pulp. 34.8 55.1 13.6 16.0 4.0 2.25 3.50 97 1, Standard white was the color a t which larger amounts of bleaching powder solution failed to improve the color.
. . . ..... .. . .. .
.. . .. .
of bleaching powder (35 per cent available chlorine) used in producing each of the bleached pulps and the yields of bleached pulp obtained are given in Table 11. TABLE I1
-.---
Cook No.
2
SODA PULP-Bleaching Powder Yield Per cent Per cent 0 33.8
3
7 15
32.8 32.5
0 12 20
42.8 41.9 40.7
.-SULFATE PULP---Bleaching Powder Yield Per cent Per cent 4 0 39.0 6 38.7 15 39.2
Cook No.
5
0 10 25
48.2 47.6 46.2
The figures for bleaching powder are based on the bonedry weight of the unbleached pulps, while the figures for yields are based on the bone-dry weight of the original wood chips. CHEMICAL TESTS Comprehensive chemical studies were made on each of the pulps indicated above by Messrs. D. E. Cable, M. W. Bray, and J. A. Staidl, under the supervision of Dr. S. A. Mahood. The chemical constants determined were those employed by Schorgerl in the analysis of certain American woods, together with certain additional tests such as lignin and a-,8-, y-cellulose of the chlorinated residue. Their value is dependent on operating under closely regulated conditions, and a complete description of the methods used and directions for operating will be given in an article by Messrs. Bray and Staidl entitled "Methods of Analysis of Wood Pulps by the Forest Products Laboratory." I n Table I11 are given the results of the determinations of moisture, ash, cold-water-soluble, hot-water-soluble, alkali-soluble, acetic acid by hydrolysis, and ether extract, TABLE I11 (Values given in per cent)
.. .
8.8 3.7 10.0 3.0
D&
Bleaching Powder Necessary Cook t o Bleach Per tostandard cent White Pulp per
33.8 42.8 39.0 48.2
23 60 18 60
to slight differences in washing the pulps during the manufacturing operation. The solubility of the unbleached pulps in 1 per cent sodium hydroxide solution are very low, which would be expected upon consideration of the fact that the pulping operation is an alkaline digestion. The bleaching operation, however, renders considerable amounts of the pulps soluble in alkaki.. The amount of alkali-soluble constituents formed increases very slowly with small amounts of bleach, but, after 6 per cent of bleach is passed with well-cooked pulps and 12 per cent, with kraft pulps, the increase in solubility is very rapid, indicating that this test would be useful to detect the occurrence of over-bleaching The presence of alkali-soluble constituents long before satisfactory color is obtained indicates that the cellulose material is being degraded as well as the coloring matter, and suggests the desirability of improved method8 of bleaching. The extremely small amount of acetic acid by hydrolysis indicates the removal during digestion of a large proportion of what acetyl groups occur in spruce. The ether extract, consisting of the waxes, fats, resins, etc., is extremely low in all the pulps except those from Cook 5. I n Cooks 2, 3, and 4 there seems to be a tendency to form ether-soluble constituents to a slight extent by bleaching. The differences, however, are small, and to a large degree may have been introduced in shredding the pulp in a mechanical shredder. I n Cook 5 the relatively high results seem to indicate that the difficulty of washing what would be termed a semi-cooked pulp has resulted in insufficient washing. The results of the remaining determinations are given as follows : Pentosan, methylpentosan, furfuroids, methoxy groups, cellulose, and lignin. (Table IV.) a-,P-, and r-cellulose, pentosan, methylpentosan, and furfuroids in the chlorinated residue reported as cellulose. (Table V.) TABLE IV (Values given in per cent)
2
Soda
0 7 15
3.48 0.90 1.27 0.62 4.94 0.91 0.51 0.08 5.66 1.22 0.45 0.18
2.46 0.06 0.41 3.40 0.06 0.52 9.81 0.04 0.76
3
Soda
0 12 20
3.91 1.12 0.71 0.26 6.26 0.92 0.58 1.07 5.79 0.90 1.27 1.21
2.81 0.07 0.49 4.93 0.06 1.10 6.92 0.04 0.71
4
Sulfate
0
6 15
3.64 1.01 1.23 0.82 5.74 0.83 0.00 0.00 5.49 1.21 0.00 0.00
2.18 0.06 0.63 2.28 0.03 0.89 8.51 0.04 0.93
0 10 25
4.89 1.16 1.25 0.40 2.62 0.101 1.65 6.04 1.27 0.59 0.00 3.61 0.04 1.42 5.97 1.40 1.23 0.91 14.02 0.04 1.10
5
Sulfate
Whit; spruce wood 0.2 2.3 3.8 8.8 1.6 1.3 1 Result high and check determination was unfortunately lost.
The results of ash determinations indicate, as would be expected, that most of the ash in the wood is retained by the pulp, in addition to certain amounts of ash from the cooking liquor, bleach liquor, and water retained through unavoidable irregularities in washing. The results of both cold- and hot-water-soluble determinations indicate soluble impurities in negligible amounts, due 'THIS JOURNAL, 9 (1917), 556.
2
Soda
3
Soda
4
Sulfate
5
Sulfate
White spruce wood
0 7 15 0 12 20 0 6 15 0 10 25
3.82 3.98 4.09 7.77 8.24 8.20 6.05 7.67 7.17 10.04 10.07 9.90 11.9
1.25 1.66 0.63 1.14 1.18 1.35 1.07 1.35 1.62 0.92 0.64 0.85 1.9
2.54 2.76 2.54 4.82 5.09 5.12 3.79 4.51 4.22 6.09 6.05 6.00
...
0.47 0.26 0.29 0.89 0.57 0.32
...
0.24 0.18 0.68 0.26 0.25 5.3
96.20 2.11 97.16 2.66 97.05 2.22 93.17 4.03 94.26 5.86 94.77 4.55 96.17 1.8% 95.68 3.43 95.40 2.64 94.56 3.39 94.00 5.55 94.56 4.04 58.6 28.3
The pentosan content as indicated by the pentosan, methylpentosan, and furfural determinations is reduced by alkaline digestion. The soda pulps are lower in pentosan than the sulfate, but when the yields of pulp are considered the sulfate process, with the same reduction of yield, produces a pulp lower in pentosan. Bleaching does not reduce the value
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
938
TABLEV (Values given in per cent)
2 3
Soda Soda
$
lii
0 12 20 4 Sulfate 0 6 15 5 Sulfate 0 10 25 White spruce wood
80.30 55.93 51.50 85.66 60.57 53.01 81.80 72.20 62.95 84.20 64.70 56.87 63.6
13.27 34.22 37.80 7.81 34.19 35.07 10.31 18.72 26.90 6.31 23.98 31.55 10.4
6.43 9.85 10.70 6.53 5.24 11:92 8.07 9.08 10.15 9.49 11.32 11.58 26.1
3.42 3.87 3.41 7.31 7.45 6.80 5.81 6.95 6.20 9.96 8.30 8.46
...
1.54 1.88 1.92 1.52 1.33 1.50 1.62 1.01 0.97 1.29 1.70 1.46
2.33 2.71 2.48 4.59 4.63 4.32 3.85 4.28 3.84 6.10 5.26 5.27
given by these tests, but since oxycellulose’ also yields furfural the indications of these tests for bleached pulps are not so illuminating. The methoxy content of both soda and sulfate pulps are very low and indicate the absence of lignin. Sulfate pulps are much purer than soda pulps in this respect, and even Cook 5: which would be regarded as only semi-cellulose by European authorities. is remarkably low. Bleaching reduces the amount of methoxy groups still more. The yields of cellulose by the chlorination method of Cross and Bevan are of particular interest because the paper maker is interested in a white fibrous product of certain physical properties and resistant to the action of the atmosphere or light. Whether the fiber has the same constitution as cotton cellulose does not concern him. The residues obtained from t h e chlorination method meet his requirements, and if the laboratory procedure could be extended to commercial operation without undue cost it undoubtedly would be used. The results of this determination indicate that both soda and sulfate pulps are capable of giving very high yields of bleached fiber of most satisfactory white. The sulfate pulps give much higher yields, however, when the original weights of wood are considered. The lignin determinations also indicate that sulfate pulps are much superior to soda pulps when the weight of wood used is considered. The fact that mild bleaching increases the lignin determinations while further bleaching reduces them is interesting, and indicates that addition products are probably first formed and are later removed, and suggests the feasibility in commercial operation of removing them before the bleaching operation is continued. The W, p-, and 7-cellulose determinations on the residue from the cellulose determination indicate that the or most resistant portion of the residue is diminished, the more drastic the cooking conditions or the further the bleaching is carried. The 8-portion is increased by increased digestion, and also by bleaching. The 7-portion seems to be reduced by more drastic cooking but bleaching tends to increase it. The reduction of the amount of so-called a-cellulose by both alkaline digestion and bleaching made it appear desirable to make similar determinations on the unbleached pulps. These were later made on all but Cook 4,of which none remained. The results for soda pulps were as follows: (Y-
COO^^................
Cook3
................
a
B
78.20 85.25
5.46 7.15
Y
16.54 7.60
The well-cooked soda pulp is lower in a- and &cellulose than the residue from the same on chlorination, but much higher in 7-ceUulose, on account of the fact that the various steps in the chlorination method probably dissolve a considerable proportion of it. With the raw soda pulp, Cook 3, the results differ much less from the residue from chlorination. 1 Browne,
“Handbook of Sugar Analysis,” p. 452.
Vol. 13, No. 10
The a-determination on the unbleached pulp of Cook 5, the raw sulfate cook, was 86.50 per cent; considerably higher than the same for the residue from chlorination and the highest of any in the series. Unfortunately an accident prevented the determination of the 8- and y-constituents. The data, as far as they go, indicate the greater effectiveness of the sulfate process in isolating the resistant fibrous constituents of wood with the least loss of material. The pentosan, methylpentosan, and furfural determinations on the residue from chlorination indicate that the chemical operations through which the pulp has passed in this method has reduced the constituents represented above but little, if a t all. It is, however, further evident that, from the standpoint of the manufacture of bleached pulp, the presence of these constituents may be ignored. The study of the chemical data makes i t appear evident that there is not any substance in considerable quantity that causes the color or difficulty in bleaching soda or sulfate pulps. A comparison of the bleachability and yields of the pulps under discussion will further emphasize the point.
Process Soda Soda Sulfate Sulfate
Yield Cook No. Per cent 2 33.8 3 42.8 4 39.0 5 48.2
Bleach Required Per cent 23 60 18 50
Yield Chlorinated Residue Unbleached Pulp Bleached Pulp Per cent Per cent 32.5 32.0 39.8 40.0 37.5 39.0 45.6 44.5
I n the case of Cook 5 a yield of 44.5 per cent of bleached pulp was possible, using 50 per cent of bleaching powder. I n order to obtain a pulp that could be bleached with 18 per cent of bleaching powder a reduction of yield to 39 per cent was necessary. The residue obtained by chlorination was 45.6 per cent in the former case, against 37.5per cent in the latter. It is apparent that in order to produce a pulp that could be bleached with reasonable amounts of bleaching powder, 8 . 1 per cent of white, fibrous cellulose material has been destroyed, or over 21 per cent of the pulp obtained. The work clearly indicates that the problem of using sulfate or soda pulps for the better grades of light colored papers lies in the bleaching rather than in the cooking operation. The use of caustic soda alone in digestion is also shown to be much more inefficient in resolving wood to bleachable pulp than the use of caustic soda with the addition of some reducing compound, such as sodium sulfide. The chemical data furthermore emphasize the desirability of carrying on the cooking operation as mildly as possible and leaving as much for the bleaching operation as can be accomplished without degrading the cellulose. The amount of material that must be removed is extremely small and is clearly of the nature of a dye. The procedure used in making analytical determinations of cellulose would be ideal but unfortunately cannot be considered on a commercial scale. Combinations of oxidation and reduction with washing between steps, have been tried with promising results. An account recently published’ of some work done on loblolly pine and red gum describes how the bleach consumption of sulfate pulps obtained with a yield of from 40 to 42 per cent was reduced from 30 per cent to 15 per cent with whiter pulp, by dividing the bleaching operation into two steps and washing between each step. Yields of 45 per cent have since been bleached with 18 per cent of bleaching powder, using the same methods. These results give additional evidence to the value of modifying the bleaching operation and it is believed that further work now in progress will make possible higher yields with satisfactory quality. 1“Book Paper from Southern Pines and Gums,” Paper, 27, No. 11 (1920); Paper Trade J . , 71, No. 22, 34; Southern Lumberman, 98, No. 1318, 47; Paper Ind., 2, 1527.
Oct., 1921
THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY CONCLUSIONS
The chemical characteristics of soda and sulfate pulps indicate that they are a very pure form of wood cellulose and capable of high yields of white fibrous and resistant material. The sulfate process is much more efficient than the soda process in yielding a bleachable pulp from coniferous wood. The coloring matter in pulps is of the nature of a dye and can be removed without materially reducing yields. Most of the action in cooking to reduce bleach consumption is to dissolve and degrade the cellulose.
939
Modifications in bleaching methods give promise of greater result,s than modifying cooking methods. Modifications in which the bleaching operation was divided into two steps, with washing between steps, cut the bleach requirement in two. Pulps of better quality, both from physical and chemical considerations, are obtained by cooking the wood as little as possible in isolating the fibers and by accomplishing as much of the burden of purification as possible in the bleaching and washing operations.
The Determination of Vanadium and Chromium in Ferrovanadium by Electrometric Titration' By G . L. Kelley, J. A. Wiley, R. T. Bohn and W. e. Wright
MIDVALE STEEL &
ORDNANCE
C0.p NICETOWN PLANT,
The object of this paper is to describe a method for the determination of vanadium in ferrovanadium not subject to interference by chromium, which is so often present. Kelley and Conant2 described the electrometric titration of vanadium following oxidation with ammonium persulfate and silver nitrate, but the method did not provide against the possible presence of chromium. Kelley and the collaborators3 above named described a method for the selective oxidation of vanadium in steel in the presence of chromium, using nitric acid as an oxidizing agent. At that time, however, we were not prepared to recommend the application of our procedure to the determination of vanadium in ferrovanadium. Since then its application t o the analysis of this alloy has been studied. PRELIMINARY EXPERIMENTAL WORK DETERMINATION O F VANADIUM I N AMMONIUM VANADATE-
A large volume of solution was prepared from ammonium vanadate described by the maker as C. P. This was analyzed by two methods. I n the first, the vanadium was determined by titrating the solution with ferrous sulfate and dichromate, taking as the end-point the point of greatest change in the oxidation-reduction potential. The potassium dichromate solution was made from a C. P. salt which had been recrystallized and fused. It was also compared through the ferrous sulfate with permanganate which had been standardized against sodium oxalate. The average difference between these standardizations was less than one part in one thousand. I n the second method, 100 cc. of the ammonium vanadate solution were placed in a flask, with an equal volume of water and 5 cc. of sulfuric acid (sp. gr. 1.58); and treated with sulfur dioxide for 20 min. a t the boiling temperature. The excess of sulfur dioxide was removed by passing purified carbon dioxide through the still boiling solution for an additional 20 min. Two hundred cc. of a boiling water solution containing 50 cc. of sulfuric acid (sp. gr. 1.58) were next added, and the mixture was titrated hot with 0.05 N permanganate using the potentiometric end-point. Eight determinations by the first method gave 0.1273 and 0.1274 g. of vanadium in 100 cc. of solution, the average result being nearer 0.1273. The solutions titrated with permanganate after sulfur dioxide reduction did not agree so well. The results ranged from 0.1269 to 0.1275, averaging 0.1272. The condition most favorable t o titration with ferrous sulfate is an acid concentration of about 50 cc. of sulfuric acid (sp. gr. 1.58) in a volume of 350 cc. at a temperature of 5" @. Under these circumstances the change in potential for 0.05 cc. of the ferrous sulfate solution (23 g. ferrous ammonium sulfate in one liter) is about 50 mv. at the end-point. 1 Received
April 13. 1921. A m . Chem. Soc., 88 (Isle), 349. *Tars JOURNAL, 11 (1919), 632.
* J.
PHILADELPHIA, P E N N S Y L V A N t d
When the vanadyl sulfate is titrated at 80" C. with permanganate in a similar acid concentration, the change of potential is about 60 mv. Under these conditions the color of permanganate is not visible until about 0.20 to 0.25 cc. more of the permanganate solution has been added. The poorer quality of the work done with permanganate may be due t s the incompleteness of the reaction between the permanganic acid and vanadyl sulfate, and the results are, doubtless, affected by the exposure of the hot solution to air during titration. NITRIC ACID OXIDATION-The solution of vanadyl sulfate, standardized as above, was used to check further the degree of oxidation effected upon vanadyl salts by nitric acid. 13 our earlier paper on the selective oxidation of vanadyl salts by nitric acid in the presence of chromic salts, it was suggested that the vanadium be considered approximately 99 per cent oxidized. Our more recent work leads to the belief that the degree of oxidation is more nearly 99.5 per cent. With the object of simulating conditions which would obtain if the work were done upon ferrovanadium, solutions were prepared containing 0.3 g. of pure iron, 0.1273 g. of vanadium as ammonium vanadate, 25 cc. of sulfuric acid (sp. gr. 1.58), 40 cc. of nitric acid (sp. gr. 1.40), and water enough to make the total volume 200 cc. The iron was first dissolved in the sulfuric acid and water in the presence of the ammonium vanadate, thus reducing the latter to vanadyl sulfate. The mixture was boiled for 1 hr., a t such a rate that the volume was 100 cc. at the end of the period. It was then cooled to 5" C. and titrated electrometrically with ferrous sulfate and potassium dichromate. Out of twenty-four determinations made, the value found for percentage oxidation was 99.3 in four cases, 99.5 in eleven, 99.6 in six, and 99.7 in three. The average was 99.5 per cent oxidation, with a maximum variation of 0.2 per cent above and below. We have previously shown' that chromium is not oxidized under these conditions. We have made a further investigation of the effect of conditions upon the oxidation of vanadium by nitric acid, but inasmuch as our results were largely negative, they need not be described in detail. Oxidations conducted in flasks a t the boiling temperature, with air passed through for 6hrs., did not show consistently higher oxidation than solutions boiled 1 hr. in beakers covered with watch glasses. When air was excluded, the results were slightly lower. METHODFOR DETERMINING CHROMIUMAND VANADIUM IN FERROVANADIUM Dissolve 3 g. of ferrovanadium in 75 cc. of nitric acid (sp. gr. 1.13). When solution is nearly complete, add 10 cc. of hydrochloric acid (sp. gr. 1.20). When the amount of silicon is large, i t may be convenient to add a few drops of 1 LOG.
ci).
