« AnteriorContinuar »
operation of chloridising roasting. All students in this stage ought to be able to make a sketch of the hand-worked four or five hearth reverberatory furnace required in this question. Q. 11. How would you treat an ore of the following composition for the extraction of the lead it contains ? Galena
50 per cent.
50 per cent. Give the chemical reactions which take place. Only two correct answers. In the majority of the answers it was proposed to flux the calc spar, whereas it should be separated by dressing, and the dressed product then treated in a furnace of the Flintshire type. Q. 12. State the principles and chemical reactions on which the processes
for the extraction of mercury from its ores depend. Great weakness shown in the answers. Instead of a statement of the principles, the process and plant were usually described; the plant given being in every case an obsolete form of furnace and condenser, now only of historic interest. Answers of this character are never awarded marks.
SECTION IV. Q. 14. Describe and make a sketch of a water-jacketed blast furnace for
smelting copper ores. Why are water jackets used ? There were only four good answers to this question, but it was not attempted by many candidates. The modern water jacket furnace is of such great importance and in such extensive use that every student, even in Stage 1, should be acquainted with its form and the principles on which it is constructed, and there can be no valid excuse for the ignorance shown by the candidates from some of the schools in their answers to this question. Q. 15. Describe the process of refining tin. State the changes which
take place in the operations. Several candidates omitted the operation of liquation which is essential before the metal is “boiled" or tossed." Q. 16. Name the common alloys in which zinc is an important, but not
the chief constituent. Give their compositions and industrial
Some fairly good answers. In the others the compositions given were too often mere guesses, as were also the industrial uses of the alloys.
STAGE 2. Results : 1st Class, 27 ; 2nd Class, 73 ; Failed, 39 ; Total, 139. The number of candidates taking the examination in this stage was considerably greater than last year, 139 papers having been received, as compared with 115 in 1905. The general standard reached was on the whole better than last year,
in fact, many of the answers to questions in this stage were more complete and showed a wider knowledge of the subject tban some in Stage 3. That the identification of samples of ores and metallurgical products still leaves much to be desired will be evident from the fact that typical samples of ganister were frequently described as limestone, galena and cerussite as grey iron, brass as copper, and white iron as copper matte.
Some of the sketches were good, but as a rule they were poor and inaccurate. In not a few instances, the same mistakes occurred in a number of papers from the same school, which indicates either that inaccurate díagrams or faulty text books are einployed for teaching.
In the identification of specimens, also, similar mistakes often occur throughout an entire school. Such mistakes cannot be coincidences, and appear to indicate that a limited number of specimens only are shown the students. It cannot be too strongly impressed upon teachers, that not only should an ample supply of specimens be provided for the students, but they should be afforded facilities for actually handling them.
A striking point revealed by the examination is the ignorance of many of the candidates of the composition of the more common alloys. German silver, in several instances, was described as an alloy of silver and copper ; soft solder as a mixture of lead and zinc or tin and zinc, and ferro-nickel as a steel containing 5 per cent of nickel.
SECTION I. Q. 21. Distinguish between the following metallurgical terms :-(a)
Malleability” and Ductility”; (6) “ Forgeability and
Weldability”; (c) Give characteristic examples of each. In most cases this question was answered correctly; a few candidates, however, confused the terms “Forgeability" and "Weldability” and in two instances the candidates thought that an essential feature of welding was that the metals should be cold. Q. 22. How much brown iron ore (2 Fe,O3, 3 H,O) will be required to
convert one ton of a gangue of the following composition into
a mono-silicate slag? Calc Spar (CaCO3)
50 per cent. Quartz
50 Atomic weights : Fe=56, Ca=40, Si=28, C=12. Only three of the 31 candidates who attempted this question obtained a correct result, several lost a few marks for arithmetical errors, but the majority failed to obtain good marks either from their not knowing the general formula for a mono-silicate or from their attempting to produce one with Fe,0, in its composition. Q. 23. Describe, with the aid of sketches, a modern water-bottom gas
producer and give the approximate composition of the gas you
would expect to obtain from it. Forty-two candidates attempted this question, and in a few instances good sketches and descriptions were given, but the majority of the answers were poor. Some candidates thought the producer they described would give a gas mainly composed of either hydrogen or carbon dioxide, while several considered that nitrogen would not enter into its composition at all.
Q. 24. Name and briefly describe the six specimens submitted to you.
Although the specimens were perfectly typical ones, no less than 70 candidates failed to obtain half marks. The specimens, which were of a simple character, were :-Iron Pyrites, Ganister, Blue Metal, Galena and Cerussite, White Iron, and Brass. As was pointed out in last year's Reports, it is still evident that facilities are not afforded the students in many institutions for recognising ores, metallurgical products, and materials. In addition to adequate facilities for handling specimens at schools, the students should be encouraged to make collections of their own. They should also be taught to make rough tests for the hardness of the materials with a pocket knife, then such mistakes as describing ganister as limestons, blue metal as blast furnace slag, and brass as chromium are hardly likely to occur. A small pocket lens would aid the students greatly in identifying specimens.
From the answers given to this question, it is evident that very little attention is given to this important branch of the subject in the majority of schools.
SECTION II. Q. 25. Describe fully, with the aid of sketches, an ordinary Whitwell
hot blast stove. A few good answers were given to this question, but the majority were weak. Some students gave the original form of Whitwell stove, while others described the old pipe stove. Some of the sketches were good.
Q. 26. Give an account of a modern automatic method for charging a
blast furnace smelting iron ores. Make a sketch of the appli
The same remarks apply to this question as to a similar one set last year. In many cases the ordinary “cup and cone was described as an automatic method for charging a blast furnace. Several candidates from one school described with sketches an ordinary bucket elevator for this purpose. It is hardly possible that a number of mistakes of this nature can be due entirely to the imagination of the students. Q. 27. In what respects does the Thomas-Gilchrist or “basic” process
differ from the Bessemer or "acid ” process ? Describe a con
verter used for the basic process. Some really good answers were given by candidates who were evidently well acquainted with modern steel works practice. On the whole this question was well done. Q. 28, Classify the processes employed in the manufacture of steel.
State the principles and chemical reactions on which each is
based. l'his question, like the last, was often well answered and good marks were obtained by many of the candidates who attempted it. The chemical principles and reactions were, however, too frequently omitted.
plant for the treatment of sands.
of gold and silver bullion by sulphuric acid depends. Give an
outline of the operations.
to obtain marketable lead and silver :-
45 Calc Spar
Silver, 20 ounces per ton. Not well done by the majority of those who attempted this question. everal candidates suggested the concentration of the lead by means of Wilfley, and other concentrators, in spite of the high percentage of cerussite present.
In several cases, where treatment of the ore in a blast furnace was suggested, the addition of iron ore as a flux was omitted. Q. 32. How may the silver in a pyritic silver ore be made soluble in
water and in brine respectively ? How may the silver solutions be treated for the production of the
metal in ingots ?
The students who attempted this question generally gave their answers accurately. In a few instances the Ziervogel process was not given for converting the silver in a pyritic ore into sulphate, and some did not mention the possibility of having to add more pyritic material in order that the roasting should be effective.
SECTION IV. Q. 33. How would you smelt copper refinery slag in order to obtain the
copper it contains ? Explain the chemical changes which take
place by equations. Only attempted by 16 candidates, of whom only seven gave passably good answers. Most of the students preferred to treat the slag in the fourth operation of the Welsh copper process, for the production of "white metal.” In only two cases was the possibility of smelting in a blast furnace mentioned. Q. 34. Describe and make a sketch of a modern barrel converter for
Bessemerising, copper regulus. Give a brief account of the
working of a charge. Some good answers. Several candidates described an ordinary vertical converter with bottom tuyères, and lost marks accordingly. Q. 35. State fully the conditions which are essential in distilling zinc ores
in order to obtain the zinc as metal. Why cannot a blast
furnace be used instead of retorts? Many candidates enumerated the essential conditions for the distillation of zinc ores satisfactorily, but they failed to show why it is practically impossible to use a blast furnace instead of retorts. A few only mentioned the facts that both carbon dioxide and air will oxidise volatilised zinc and that the large quantity of escaping gases from a blast furnace would render the condensation of the zinc as metal impossible. Q. 36. Give an account of the physical properties, composition, and chief
uses of the following alloys :-Muntz metal, German silver, soft
solder, and ferro-nickel. Only ten satisfactory answers were given to this question. It is surprising to note that several candidates in this stage had no idea of the compositions of the four simple alloys given in the question : several thought Muntz's metal was composed of copper and tin, while others thought soft solder was composed of lead and zinc.
STAGE 3. Results : 1st Class, 12; 2nd Class, 21 ; Failed, 25; Total, 58. There is an increase of 8 in the number of papers sent ir. as compared with last year, and it is satisfactory to note that there is a marked improvement in the quality of the answers of the candidates generally. The weakest point in all the papers, with two or three exceptions, was the recognition of metallurgical materials (Q. 42). This was deplorably bad, although the specimens were all extremely characteristic, and comprised only materials in every-day occurrence in works. It was even worse than in Stage 2.
In the answers to the other questions, obsolete processes and plant occurred much less frequently than hitherto.
SECTION I. Q. 40. State fully the physical characters and composition which coke
should possess for use in a blast furnace smelting iron ores for
Bessemer pig. The answers as a rule were only moderately good. No mention was made in many papers of ash and phosphorus, and the percentages of carbon given in some can only have been mere guesswork.
Q. 41. How would you proceed to obtain a continuous record of the
variations in temperature of a reverberatory furnace ! Describe the pyrometer you would employ and state how you would
calibrate it. Several good answers, but the majority of candidates can never have seen, and certainly not used, a recording pyrometer.
Q. 42. Name and briefly describe the six specimens submitted to you.
Attention has been called above to the extremely bad answers to this question.
The following examples will suffice to show the ignorance of some of the candidates :
Copper refinery slag containing shots of copper was variously named copper regulus, tap, cinder, brown hæmatite, tinstone, white cast iron, iron pyrites and mispickel ; while coarse metal was said to be cinnabar, ferromanganese, grey slag from lead smelting, zinc blende, steel furnace slag, tap cinder, magnetite, wolfram, tinstone, &c.
If candidates would only try the hardness of the specimens, as has been already pointed out under Stage 2, most of these glaring mistakes would not be made.
19 candidates recognised only one of the six specimens and 10 failed to recognise any.
SECTION II Q. 43. Describe and make sketches of the lower half of a modern blast
furnace for smelting iron ores, showing two methods of cooling
the boshes. This easy question was attempted by only about one-third of the candidates. There were a few excellent answers, but the others showed a very imperfect acquaintance with the construction of a modern watercooled bosh. Q. 44. Describe the manufacture of steel as carried on in a tilting furnace
by a continuous process. State the chemical changes which take
place from charging to tapping. Generally well answered. Q. 45. How are malleable iron castings produced ? Explain exactly why
the final treatment, to which the castings are subjected, renders
them malleable. The method of preparing malleable iron castings was generally given correctly, but the cause of the malleability was in too many answers attributed solely to the removal of carbon and not to the change of the carbon from the combined to the finely graphitic state.
SECTION III. Q. 47. Give a brief account of the cyanide plant you would erect, and
the treatment you would adopt for the extraction of gold from
an ore, the whole of which has been ground to slimes. Answers very poor ; only 7 candidates out of 30 who attempted the question obtained more than half marks. The treatment of gold ores by the cyanide method and the arrangement of the plant is evidently very imperfectly taught in most schools. The majority of the candidates had no knowledge of either the decantation or the filter press method, and confused the treatment of slimes with that of sands. Impracticable arrangements of the plant were sketched. Some gave ferrous sulphate as the precipitant for the gold. Q. 48. Describe and make a sectional sketch of the lower half of a
modern rectangular water-jacketed furnace for smelting lead ores. How does the hearth differ from that of a copper smelting blast furnace ?