990 THE COLLIERY GUARDIAN. May 25, 1917. CURRENT SCIENCE The Constitution of Pyrites. Mr. W. H. Goodchild, writing in the Mining Maga- zine, calls attention to the constitution of pyrites. Pyrites is usually represented by the formula FeS2, and consequently as a molecule built of three atoms. It is typical of a large class of natural sulphide minerals, which have the chemical property, that when heated to moderate temperatures they undergo more or less complete dissociation into a simpler sulphide*, or matte constituent, and free elemental sulphur. A consider- ation of this reaction is a convenient starting point for a discussion of the constitution or degree of com- plexity of the pyrites system. As sulphur is a con- stituent of both products of this reaction, and is com- mon to the whole class of compounds of which pyrites and the lower sulphide, or iron matte, may be con- sidered as the fundamental types, it is pertinent to the question to review as briefly as possible some of its physical and chemical characteristics. These charac- teristics are striking, and the element is in many ways peculiar. Experiments carried out at the Carnegie Institute at Washington indicate that the pyrrhotites are solid solutions of sulphur in ferrous sulphide, and from general chemical considerations this view appears to be well founded. There seems to be no ground for believ- ing that any serious decrease in the degree of associa- tion of the element is brought about by solution in ferrous sulphide, but on the contrary, analogy renders it highly probable that the pyrrhotites contain dis- solved sulphur in the form of highly associated mole- cules. This view is supported by consideration of the densities of the pyrrhotites and other “higher” sulphides of iron. The synthetic pyrrhotites prepared at Washington do not appear to be absolutely identical in constitution with the naturally occurring minerals, the latter apparently being of higher specific gravity for a corresponding composition. It was noted at Washington that as the quantity of dissolved sulphur increased, the density of the resulting pyrrhotite diminished, whereas the opposite appears to be the case for the natural minerals, as far as can be judged from published analyses. Hitherto little attention has been given to the comparative study of the relative densities of the natural sulphides and other ore minerals as a means of elucidating the problems of their molecular constitutions,^ and the processes con- nected with their formation. The comparative inves- tigation of densities has shown itself to be one of the highest importance in the development of our know- ledge of molecular chemistry, and has already yielded so many and such brilliant results in theoretical chemistry, that it would appear to be worthy of more serious consideration in connection with the study of minerals and the processes whereby minerals are formed under natural conditions. A simple method of analysing some of the volume relations of the natural sulphides, and one that brings out some interesting and suggestive features, is to calculate the diminutions in volume that occur as the result of combination of the elements or compounds, and to express the contraction in terms of sulphur density. For instance, the difference between the solid specific volume of natural FeS and that of pyrites may be considered as approximately the volume occupied by the additional sulphur, and from this its density may be calculated. The assumption is that the matte constituent of the system, FeS, is closely compacted and of negligible compressibility, an assumption that is probably not very wide of the mark in view of its density, and its specular and metal-like characteristics, the last two properties especially indicating a close packing of the molecules of the substance. The den- sity of the sulphur dissolved in the synthetic pyrrho- tites prepared at Washington, according to this method of computation, is roughly 2-5, or about equal to that of sulpuhr in chalcocite or covellite; whereas in the natural pyrrhotites it appears to be about 6, or approximately three times as dense as common ortho- rhombic sulphur, and identical with that of the second portion of the sulphur in the pyrites system. Since diminution in volume or increase in density is so frequently a result of polymerisation, it seems pro- bable that the natural pyrrhotites contain dissolved sulphur polymerised to a "degree similar to that of the second portion of sulphur in the pyrites system, and greater than in the case of the synthetic preparations. There is an important experimental fact that indi- cates, though not perhaps conclusively, that the natural pyrrhotites are not, as might be inferred from this density relationship, solid solutions of pyrites in troilite or FeS, for, using the commonly accepted terminology, without prejudice to the fundamental point of this discussion, the disulphide of iron, or pyrites, is insoluble in hydrochloric acid, whereas the pyrrhotites are easily attacked by this reagent, leaving a residue not of pyrites but of sulphur. The natural pyrrhotites and the synthetic products appear to be identical to the extent that both are apparently of the nature of solid solutions of sulphur in ferrous sulphide, although the differences in density point to differences in the molecular condition of the dissolved sulphur. On the other hand, the state of the sulphur in the natural pyrrhotites would appear from the density relationship to be similar to that of the second portion of sulphur in pyrites. The very large contraction in volume that occurs when pyrites is formed from FeS by the addition of sulphur is parti- cularly noteworthy, as it appears to be altogether exceptional when compared with the corresponding, phenomena presented by other natural sulphides. A cu. cm. of pyrites contains a greater weight of sulphur that a cu. cm. of solid orthorhombic sulphur—a fact that does not seem to have attracted particular atten- tion hitherto. Pyrites thus appears to be a natural AND TECHNOLOGY. device for cramming the maximum quantity of sulphur into the minimum space, and from this point of view it is of special geological interest. A summary review of the density relationships of sulphur, the pyrrhotites, and pyrites, taken in conjunc- tion with the collateral chemical evidence, thus leads directly to the conclusion that they are all highly asso- ciated arid molecularly complex substances, and that such simple formulse as FeS2, Fe7S8, etc., do not repre- sent their true molecular constitutions, but only frac- tions of these. Consequently, the molecular volumes are very much greater than would appear from a con- sideration of the commonly accepted formulae for these mineral systems, such as are given in text-books bf mineralogy. The relatively large size and complexity of the unit systems of these sulphides is of immediate geo-chemical interest, and significance in connection with the processes of their precipitation from such dilute solutions as are thought to be operative in the concentration of the useful metals into ore deposits. It suggests, for instance, how porosity of a rock may conduce to local precipitation from a solution by the ultra-filtration of the smaller molecules of a solvent such as water from bulky molecules such as these sulphide systems appear to be. Potash as a By-Product from the Blast Furnace. In the discussion on Mr. R. J. Wysor’s paper before the American Institute of Mining Engineers, Mr. C. Catlett stated that certain red haematites in Eastern Alabama (locally known as “grey ores”) give a K2O contents of 2-08 per cent., which, with a basis of 45 per cent, metallic iron, would furnish for each unit of iron 0*046 unit of potash. Out of 106-67 lb. of -potash charged into the furnace per ton of iron, the loss from fumes, etc., dust catcher, top furnace, and slag amounted to 16-24 lb., leaving 90-43 lb. to be recovered. At the Security Cement and Lime Company’s plant at Hagerstown, Maryland, with which the speaker was associated, the waste gases from the kilns are passed through a Cottrell precipitator. The balance shows that they commonly save 90 per cent, of the material that actually goes into the treater; and even if only 85 per cent, recovery were obtained, this would mean a saving of 76-86 lb. of K20 per ton of iron produced. Production of Liquid Ammonia at a Dutch Gas Works. Heer W. Meyer Cluwen, engineering chemist at Arnheim Gas Works, describes in the Dutch Chemisch Weekblad (abstracted in Gas World) the production of liquefied ammonia in order to meet the demand in Holland. Till the outbreak of war, Great Britain, Germany, but above all Belgium, were the suppliers of the liquefied ammonia consumed in Dutch cooling technics. When war broke out, the liquid, as well as the steel bottles used for its transport, were declared contraband of war, and the Dutch industry was thus totally deprived of this freezing agent. A rough calcu- lation showed that the yearly consumption in Holland might be taken as being something like 27,000 kiloms. As in the first working year 40,000 kiloms. were sold, the calculation was obviously not far from the truth, remembering the fact that the supplies were consider- ably in arrear. The situation at Arnheim Gas Works was favourable for starting this new industry, as the liquor from the works is generally worked for pure ammonia solution, and not for sulphate. Only during very recent times the high prices for sulphate have caused the introduction of sulphate production. The liquor is treated in the familiar manner for driving out the ammonia in the free state. The ammonia gas is accompanied by some air and other gaseous constituents from the liquor, as also by a con- siderable amount of water. Great care has to be taken to eliminate the water as far as possible. The allow- ance for the content of water in liquefied ammonia has been restricted in the course of years. Some few years ago it was 0'9 to 1'0 per cent., but nowadays no more than 0'4 to 0'5 per cent, is allowed. Chloride of lime cannot be made use of, as it combines with ammonia. There remain, therefore, as drying agents, caustic soda in lumps and burnt lime. Caustic soda is in these times an article that is not to be had in sufficient quantities; therefore the only remedy is burnt lime. But burnt limestone is an imperfect drier, the action being only perfect at somewhat high pressure. In general, there remains 0'9 to 1'0 per cent, of water in the liquefied ammonia. Success was ultimately obtained by adding at regular temperatures liquefied ammonia to the wet gas. The evaporation of the liquid causes a fall in temperature till —15 degs. Cent, is reached, so that the water is condensed and elimi- nated in the form of strong ammonia solution. The ammonia added in liquefied form amounts to about 7 per cent, of the total production; but it is, of course, not lost, as it circulates and returns to the com- pressor. The ammonia gas, deprived thus of the greater part of its water content, passes through two towers filled with burnt limestone lumps, a spare tower being arranged to allow afterwards for the treatment with ■caustic soda. The compressing plant does not differ from that of an ordinary ice apparatus, except that no brass or copper parts are present. The compres- sion cylinder is cooled by flowing water. The oiling is done with mineral oil, an oil separator being arranged after the compressor. The gas is compressed to from 103 to 1471b. per sq. in., and the relatively warm gas is condensed in a cooling coil, and collected in a receiver of about 70 gals, capacity. On the pressure side of the compressor there is a blowing-off tap, to allow for the blowing-off of the permanent gases, more especially air. From the receiver the liquefied gas is stored into steel bottles, after these have been evacuated by means of a small suction pump. Great care should be taken that the bottles are not completely filled. The liquid has a very high expan- sion factor at a temperature of about 66 degs. Cent., so that a rise in temperature of only 2 degs. Cent, causes almost the doubling of the pressure, rendering completely filled bottles highly dangerous. In many instances bottles have burst owing to complete filling. By regular control of the real capacity of the bottles, and close supersivion of the filling, this danger can be avoided. AIR CONSUMPTION OF DRILLS.* By R. S. Lewis. The accompanying chart is a modification of the one appearing in Hock Drilling, by Dana and Saunders, with the addition of data for hammer drills and basing the diagram on an air pressure of 901b. per sq. in. at the drill instead of 75 lb., to conform more nearly with the requirements of modern practice. Factor for other Pressures and Altitudes tg 1.2 2.1 2j0 Q9 1.9 1.8 1.3 1.5 1.4 1.0 ’17 11.6 15000 14000 13000 1300Q 11000 10000 § 9000 o 8000 « 7000 u 6000 5000 4000 3000 2000 1000 ? J______CHART GIVES FACTOR FOR DETERMINING AIR. CONSUMPTION FOR ELEVATIONS ABOVE SEA _____LEVEL AND PRESSURES OTHER THAN 90 LB.. 08 ---g-------------------------------- 0.7KL.-J_____________________L—J_________________ 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 Air Pressure at Machine. Fbunds The inclined lines are based on a sea-level datum and 90 lb. pressure per sq. in. at the drill. This gives a factor of 1; for any other altitude or pressure at drill, the factor is found at the left margin, passing there from the intersection of the inclined line of the given altitude with a vertical through the given pressure. The average consumption of air for both piston and hammer drills is given in Table 1. Hammer drills vary so in air consumption that only general figures can be given. Catalogues from drill manufacturers will give the consumption for any particular drill, and generally at 901b. pressure and at sea level. By means of the chart the consumption for other conditions can be quickly found. Table 1.—Air Consumption of Rock Drills. (90 lb. at sea level). Piston Drills. Drills. In. 2 Cu. ft. per min. 68 Drills. In. 3| Cu. ft. per min. 129 2| 87 34 3t 136 2 <2 92 161 2-»- 98 44 .. 210 24 .... 118’ 5 .. 250 3 .... 125 Stoper s Drifters Sinkers Hammei 48-55-58 40-60 38-60 ■ - Drills. Block Bitch holing cutters 25-30 15-25 Table 2.—Air Consumption Factor, drills. 1 1'0 FOR MORE No. of drills. 11 than One Drill. Factor. 7'8 2 .... 1‘8 12 .. 8'4 3 2’7 15 .. 10'3 4 .... 3'4 20 . 12'8 5 .... 4T 25 .. 151 6 .... 4'8 30 17'3 7 .... 5'5 35 .. 19'7 8 6'1 40 .. 22'0 9 6'7 50 .. 26 5 10 .... 7'3 60 30'5 In case more than one drill is used, the factor by which to multiply the air consumption of one drill to determine the consumption of a number is to be taken from Table 2. This is based on manufacturers’ state- ments. When a number are working, they are seldom all running at the same time. This table covers the requirements from one to 60 drills. * Engineering and Mining Jour^s. France’s Coal Supply.—A Proclamation has been issued respecting coal stocks. Every dealer and private person must make a return of any stock of coal which he may have on June 15 at his home or place of business exceeding 1,600 kilogs. (224 cwt.) in weight. Resuscitation After Electrical Shock. — According to a published report, Mr. W. P. Strickland, general inspector of the New York and Queen’s Electric Light and Power Company, of New York City, states that one of the men, when about to erect primary wires, was apparently killed by accidentally touching a wire carrying 2,300 volts. One of the linemen immediately took hold of the ankles of the limp body, lifting it until the whole weight rested on the neck, and letting it fall. He then took a pair of connectors and hammered the soles of the injured man’s feet without removing his shoes. Another lineman opened the man’s mouth, pulled forward the swallowed tongue (which occurs in electric shock), and was about to begin the Schaefer prone method of resuscitation, when the man returned to life. He was removed to the hospital, and is alive and well to-day, though suffering severely from his. burns. Similar cases of recovery are mentioned in connection with the plan of striking the feet without removing the boots or shoes in case of electric shock.