NEW

peared to represent the maximum combining power. Like the other combinations these possessed an ochre colour, suggesting a product resembling the iodalbose of Weyl (Zeit. Phys. Chem., 1910, lxviii., 236). This product was prepared by adding egg albumin to concentrated hydriodic acid at water-bath heat, and pouring the mixture into an excess of water. The ochre precipitate which formed was purified by solution in alkali and reprecipitation. The iodine is firmly fixed in the product, which seemed to be lacking in some of the characteristic protein reactions. In all our experiments the iodine was used only in the form of dilute HI solution, and in absence of heat no ochre-red colour was developed. The concentration of the dilute acid in evaporation possibly leads to the same or similar compounds.

Pauly and Gundermann (Ber., 1908, xli., 3999, and 1910, xliii., 2243), and others and are not to be confounded with the salts secured by treatment with weak HI. Because of the easy decomposition of the latter, however, and its marked reducing properties, iodine is liberated to be carried into the molecule.

With the hope of throwing further light on the nature of the reaction, we have repeated a number of the above experiments in such a manner as to remove the excess of acids at a low temperature. This was accomplished by adding the o2 N acid to the solid protein as before and allowing the mixtures to stand some weeks over sulphuric acid to remove most of the water. The small evaporating dishes holding the residues were then placed in bell jars over powdered sodium hydroxide to absorb acid vapours. In this manner practically all of the acid was removed and most of the water. The mixtures with HCl and HBr evaporated down without much colour, but the HI mixtures became reddish brown as before. A short, final drying in the air oven was necessary to bring to constant weight. Table XIV. shows the final weights and the halogen content of the products.

Only the larger volumes of acid were added in these experiments. (To be continued).

PERMANGANATE DETERMINATION OF IRON
IN THE PRESENCE OF FLUORIDES.
THE ANALYSIS OF SILICATES AND
CARBONATES FOR THEIR FERROUS IRON
CONTENT.*

By O. L. BARNEBEY. (Continued from p. 10).

SILICA and silicic acid were used as preventives. The silicic acid was made in the solution by adding sodium silicate to the acid solution containing ferrous iron and hydrofluoric acid (Table VIII.). Experiments 1, 3, and 6 show that moderately good results can be obtained by using silicic acid as preventive. In Experiment 2 too much silicate was added in proportion to the amount of acid present, and some of the ferrous iron was precipitated, hence the low result. Experiments 4 and 5 are included to show the relative values obtained in presence of hydrofluoric acid with sulphuric acid compared with sulphuric acid plus the silicic acid.

TABLE VIII.-Silicic Acid as Preventive.
I cc. KMnO4 0.007814 grm. Fe.
I cc. FeSO4 0'006151 grm. Fe.
Na2SiO3-

Normality.

=

=

Iron (grm.).

No.

Cc.

O'IO CC. lasted.

I.

30.0

768

бог

587

HF. H2SO. NagSiOg.

[. ΙΟ

2.

25.0

640

15.0

бо

Most of the compounds of iodine and protein described in the literature are substitution products, and are obtained by the action of the halogen, as solid, tincture, or in KI solution. The products contain from about 5 to 15 per cent iodine, but show reactions deviating from those of proteins in some respects. Such compounds have been described by Hofmeister (Zeit. Phys. Chem., 1898, xxiv., 159), Blum (Ibid., 1899, xxviii., 288), Liebrecht (Ber., 1897, xxx., 1824), Hopkins and Pinkus (Ibid., 1898, xxxi., 1312), Kurajeff (Zeit. Phys. Chem., 1898, xxvi., 462),

6. 5'0 2.0

25

0'1230 01266 +0.0036 (a) O'1230 01238 +0.0008 бо (a) Very unstable.

Granulated silica, prepared by various chemical manu facturers, was tried, but it did not work so well. The pink end-point of the permanganate was far less stable, giving tendency toward high results, perhaps owing to the more insoluble nature of the silica, or to slight impurities in the silica, or to both causes.

a

When boric acid is added to hydrofluoric acid in solution, meta-fluoric acid, HBF4, is formed, which does not dis

* Journal of the American Chemical Society, xxxvii., No. 6.

remove any air inside of the glass funnel, after which 5 cc. of 1:1 H2SO4 (HCl can be used) is added by pouring down the platinum stirring rod. If carbonates are present care must be exercised to prevent too violent action. Should soluble sulphides be present the acid is likewise added slowly to expel the H2S as completely as possible. Strong hydrofluoric acid is then added, 5 cc. to 20 cc. depending upon the size of the sample, pouring down the stirring rod. The bath is maintained at an even temperature, a continuous current of steam being expelled through the funnel until the silicate is thoroughly decomposed. If carbon dioxide is allowed to pass through the bath continuously it should be regulated so that its passage is slow, just sufficient to give direction to the current of escaping gases. Occasionally a little previously boiled water is added to the bath to maintain the water level. For this purpose a flask of boiling water should be kept constantly ready for use.

When decomposition is complete the funnel is lifted from its place, and cold (previously boiled) distilled water added immediately to the dish to dilute the solution somewhat, followed immediately by an excess of solid boric acid. The solution is stirred, then lifted from the bath. If solid organic matter is present it should be filtered through an asbestos filter using suction (a carbon funnel with a Witte plate is convenient for this purpose), and the filter washed with previously boiled distilled water. The solution is poured into a glass beaker, diluted to a convenient volume, and titrated with standard permanganate. If the solution has been filtered it is titrated in the suction flask. It is well to add some solid boric acid before titrating to give the same colour effect as usual at the endpoint. When hydrochloric acid is used for the decomposition of the sample, some substance should be added to counteract its influence when the ferrous iron is titrated. Since the hydrofluoric acid has been transposed to fluoboric acid any good preventive is applicable (Cooke, loc. cit.). Ten to 20 cc. of the ordinary preventive solution (Barnebey) used in the iron titration 80 grms. MnSO4.4H2O + 80 cc. H2SO4 (sp. gr. 1.84) + 8 cc. H3PO4 (sp. gr. 17)-per litre is effective, or the phosphoric acid may be omitted, and 160 cc. of sulphuric acid used in preparing this solution.

The above method can be easily adapted to Pratt's scheme of decomposing the silicate, which requires less time because of the application of a higher temperature. The sample is placed in a platinum crucible, carbon dioxide is conducted into the crucible by means of a platinum tube, which is inserted under one edge of the cover, acid is added, and heat applied directly to the crucible. As soon as steam is evolved copiously the carbon dioxide is shut off, hydrochloric acid added, and the cover fitted snugly to the crucible. When decomposition is complete dilute somewhat with water, add boric acid and proceed as usual.

(To be continued).

FIXATION OF ATMOSPHERIC NITROGEN.* By LELAND L. SUMMERS.

Introductory.

IN 1898 Sir William Crookes in his Address as President of the British Association very forcibly pointed out that the commercial fixation of atmospheric nitrogen was one of the greatest discoveries awaiting the ingenuity of chemists. He emphasised with very interesting figures its important practical bearing on the future welfare and happiness of the civilised races. This Address brought forcibly to the attention of engineers the fact that the existing sources of fixed nitrogen were limited, and greatly

Paper presented at a joint meeting of the American Institute of Electrical Engineers and the New York Section of the American Electrochemical Society.-From the Chemical Engineer, xxi., No. 6.

stimulated the efforts of investigators. The problem itself had been worked on for over a century, as it was known that nature fixed nitrogen of the atmosphere by means of electric discharges, and Cavendish in 1781 had shown that a small amount of nitrogen was converted into nitric acid in the combustion of hydrogen with oxygen to form water, while Bunsen in 1877 obtained favourable yields by means of gaseous explosions. The earlier efforts commercially in the art were, however, largely confined to the fixation of nitrogen for the purpose of manufacturing cyanides, and the earlier bibliography of the subject therefore deals almost entirely with these efforts.

Commercial Products of Nitrogen.-The three fundamental commercial products formed by nitrogen are: first, its union with oxygen to form nitrates, XNO3, and nitrites, XNO2; second, its union with carbon to form cyanogen C2N2 and producing cyanides XCN and cyanamids XCN2; third, its union with hydrogen to form ammonia, NH3. From all of the above products there are obtained a large number of derivatives used in the chemical arts.

The most important of all commercial products are the unions of nitrogen with oxygen, forming the nitric acid salts of commerce. These are of particular importance on account of the vast natural deposits of nitrate of sodium occurring in Peru and Chile, commonly called Chile saltpetre. Practically, this commodity is the one that sets the price for all other compounds of nitrogen, as it has been mined in Chile since 1830, and during the past twenty-five years its production has assumed vast proportions, the present annual output amounting to about 2,500,000 tons. This deposit of Chile appeared inexhaustible, and therefore there was no occasion for alarm regarding the world's supply of combined nitrogen; but after years spent in exploration work it began to appear that the Chilian deposits would be exhausted before the end of the present century, and since then all other sources of combined nitrogen have received attention.

While there are a few scattered natural deposits other than those in Chile, there is none which has at the present time a chance of competing, most of them being of limited extent and situated in inaccessible regions. In Chile the deposits are easily worked, and even after years of careless mining, with no effort to effect economies, the present cost of producing nitrate is not excessive, varying from 10 dols. to 20 dols. per ton and selling in Liverpool for about 45 dols. per ton. This leaves a profit of from 5 dols. to 1o dols. a ton on the operation, after paying the Government of Chile an export tax of about 12.25 dols. per ton. In the past thirty years this export tax has netted the Chilean Government about 500,000,000 dols. Of the total production of Chile the United States imports about 600,000 to 700,000 tons per annum, the balance being practically all shipped to European countries. Chile saltpetre has sold as high as 60 dols. a ton, but since 1909, when the agreement among the producers expired, the price has approximated 45 dols. per ton f.o.b. Liverpool, making a price of from 35 dols. to 40 dols. per ton f.o.b. Chile.

The union of nitrogen and carbon to form cyanides and with hydrogen to form ammonia are two of the earliest forms in which the combined nitrogen was utilised. Most all animal and vegetable refuse contains ammonia compounds, and these were the early sources of ammonia, and animal refuse products such as hides, hoofs, and horns were the sources of combined carbon products forming the cyanides. Until the discovery of the McArthur-Forrest process for gold extraction, the markets for cyanides were comparatively limited and there was no great effort made to produce them on a large scale. With the rapid development of this art in the recovery of the low-grade gold deposits, a sudden impetus was given to the cyanide industry, and large quantities of cyanides are now manufactured from ammonia and metallic sodium. Small amounts of cyanides for industrial purposes are recovered from the gas retort houses, but these processes are not generally applied, and no particular effort has been made to extend the processes

to the recovery of cyanides from by-product coke ovens. The greater portion of the cyanides are manufactured in England and Germany, and some 20,000 tons per annum are exported annually by these two countries. As the cyanides of sodium and potassium for gold recovery purposes sell from 300 dols. to 400 dols. per ton, they represent one of the highest prices of nitrogen directly combined with a simple element.

The third great commodity of commerce, ammonia, is utilised extensively in industrial arts, but in addition has been used for many years as a fertiliser. The annual production of sulphate of ammonia now amounts to about 1,250,000 tons, and the Liverpool price approximates that of sodium nitrate, varying from 45 dols. to 60 dols. per ton. Practically all of this sulphate of ammonia is manufactured from coal distillation either from gas house retorts or by-product coke ovens, up to the past year there having been practically no process in operation for the direct synthesis of ammonia from its compounds. All the older retort processes for the manufacture of gas recover ammonia by washing the illuminating gas with water. All by-product coke ovens likewise treat the byproduct gas for the recovery of ammonia. American coals run from o'9 per cent to 14 per cent nitrogen, or from 18 to 28 lbs. (81 to 127 kilogrm.) of nitrogen per ton of coal. In the distillation of this coal, about 20 per cent of the nitrogen is recovered from the gases of distillation, so that from 4 to 7 lbs. (2.1 to 3.2 kilogrm.) of ammonia are recovered per ton of coal distilled; this ammonia when united with sulphuric acid forms sulphate of ammonia, giving a yield from 18 to 28 lbs. (8.1 to 12.7 kilogrm.) of sulphate of ammonia per ton of coal distilled. Weak solutions of ammonia water are concentrated from the gas-house retorts and the ammonia distilled from this water by breaking down the ammonia contents with lime, the pure ammonia being then united with sulphuric acid. In many of the coke oven plants the sulphate is formed directly by passing the gases into sulphuric acid, forming the ammonia sulphate by a direct process.

In general it costs about 15 dols. per ton of ammonia sulphate to manufacture the sulphate from the ammonia, so that if ammonia sulphate is selling for 45 dols. per ton, 15 dols. of this is represented in the cost of sulphuric acid and the manufacturing, making the net ammonia cost, with profit, 30 dols. per ton of sulphate, or, as the nitrogen content of the sulphate amounts to 21 per cent the nitrogen represents an actual value of 7 cents per lb. With the great increase in the number of by-product coke ovens, there has been a greatly increased quantity of ammonia sulphate manufactured, and it would seem that under these conditions the price of ammonia sulphate will tend to diminish rather than to increase. The actual cost to the by-product coke oven plants recovering the ammonia, in addition to the 15 dols. for manufacturing the sulphate of ammonia, will approximate 10 dols. per ton, and if there is any profit to be obtained from the sale of ammonia, they can afford to recover it at this figure.

Another source of ammonia by coal distillation is from producer gas generated on what is known as the Mond system. In this process steam is admitted to the producer in excess, so that the temperature is not permitted to rise to a point where the ammonia liberated by the fuel is de composed. This excess of steam tends to protect the ammonia, and it is recovered from the producer gas by washing. In this process not only the ammonia carried in the volatile products is recovered, but also a large percentage which ordinarily remains in the carbonaceous residue of the coke oven and gas-house retort. As ordinarily distilled, about 50 per cent of the total ammonia of the coal remains in the coke residue and is not recovered. In the producer, where this coke is consumed in the presence of steam, the total percentage of recovery may be as high as 75 per cent of the theoretical nitrogen contained in the coal, so that from 15 to 20 lbs. (6-8 to 91 kilogrm.) of nitrogen may be recovered, or, in terms of ammonia sulphate, from 60 to 80 lbs. (27.2 to 36.2 kilogrın.) of

ammonia sulphate may be obtained per ton of coal consumed in the producer. This type of producer has not been extensively utilised in America, as the expense of installation is increased by the necessity of washing a very large volume of low-grade gas, the volume of gas per ton of coal consumed in the producer being about 130,000 cubic feet against about 10,000 cubic feet per ton of coal, as distilled in the coke oven.

A number of these plants have been installed in England and on the Continent, but the aggregate of the ammonia sulphate produced is not large as compared to that from coke ovens and gas-house retorts.

Available Nitrogen in Commercial Products. - The question of the available nitrogen in the various compounds has, in a measure, determined the price of the product, the utilisation in the fertiliser art being practically the basis of fixing the price. For a number of years it has been assumed that the selling price of combined nitrogen would be from 12 cents to 13 cents a lb. Thus Chile saltpetre being about 95 per cent pure, nitrate of soda would have a theoretical nitrogen content of about 16 5 per cent, or, corrected for impurities, would have about 15.5 per cent nitrogen.

As the cyanides, until recently, were not used directly in the fertiliser art, and were combined with more expensive products, their price has not been regulated by their content of combined nitrogen. The ammonia used in the fertiliser art is almost entirely used as sulphate of ammonia, on account of the cheapness of the commercial sulphuric acid and the ease of manufacture, and this product would therefore have a theoretical content of 21 per cent of nitrogen.

The above nitrogen products may be considered the fundamental commercial forms in which combined nitrogen enters the market, and while the fertiliser industry fixes the price of combined nitrogen, it is only one of the many industries in which vast quantities of nitrogen are utilised. Thus about 50 per cent of all the Chile saltpetre imported in this country is used in the manufacture of explosives, while an additional 25 per cent is utilised in the arts requiring nitric acid. Of the ammonia sulphate, a very large percentage is used directly as fertiliser, though there is a very considerable demand for use in chemical industries and such commercial applications as anhydrous and aqueous ammonia used in the refrigeration art. Practically all explosives have utilised nitrogen compounds as a prin. cipal ingredient. The earlier makers of black gunpowder used Chile saltpetre, charcoal, and sulphur, and the later so called smokeless powder utilises the oxygen-carrying property of nitrogen as well as the inherent molecular energy in the production of such high explosives as nitroglycerin, cordite, lyddite, melinite, gun-cotton, and various other nitro-cellulose compounds, and modified explosives used in industrial work, such as dynamite and various blasting powders.

Fixation Processes. In considering the fixation of atmospheric nitrogen from a commercial standpoint, the limitations will be imposed by the selling price of the natural product from Chile, covering nitrate compounds, and the selling price of ammonia sulphate, as obtained from coal distillation, affected as these prices will be by the manufacture of ammonia from atmospheric nitrogen.

In competition with the above sources of nitrogen there has been the constant effort toward the fixation or rather the utilisation of some of the vast quantity of atmospheric nitrogen surrounding us.

A list of these fixation processes would contain the names of hundreds of investigators, and from the past twenty years of effort there may develop processes which at present are still experimental; but of the various processes which have reached the state of commercial application there appear to be four distinct lines of development.

First. The production of nitric acid directly from the atmosphere by means of the electric arc. In this process