Bavaria, but have not ascertained how much this mineral generally contains; neither did Sefström nor Schultz and Bodeman determine the quantity of vanadium present in the iron ores which they investigated. Deville likewise detected the presence of vanadic acid in bauxite, an aluminiferous mineral, from Baux, in the south of France, utilised in the manufacture of aluminium. The quantity of vanadic acid present in the flower-pots of the Jardin des Plantes was not determined. To allude to some substances which usually accompany vanadic acid in clays, I will mention that titanic acid and tantalic have been both found by myself and other chemists; also phosphoric acid is very usually present in small quantities.

One hundred parts of vanadium ochre gave me on analysis: water and a little organic matter, 12.60; oxide of iron, 57-50; alumina, 500; vanadic acid, 190; phosphoric acid, 2.20; titanic acid, traces; magnesia, 0.30; lime, 0.20; carbonic acid, 0-24; silica or quartz, 20-0099-94.

Let us take 0.05 per cent. as the probable quantity of vanadic acid contained in the greater bulk of that vast geological deposit known as the London clay. At this rate one ton of London clay would contain about 1 lb. 2 oz. of vanadic acid, say 1 lb. to the ton in round numbers. If we suppose that there exists only about a million tons of this clay at the west end of London, for instance, in the Hyde Park and Bayswater districts alone, we have evidently there upwards of 445 tons of vanadic acid!

And if we calculate the quantity of vanadic acid which exists in the London clay of the metropolis, supposing London to cover fifty square miles, and taking the stratum of clay at the moderate thickness of four yards, we find that, under this city alone there lies probably far more than 303,443 tons, or about 679,712,320 lbs. weight of vanadic acid; the present price of this substance in shops where chemical curiosities are sold being about one shilling and sixpence per grain, or £32 5s. 6d. an ounce !

I have not the slightest doubt that all clays contain similar quantities of vanadic acid, and if it can be extracted with tolerable ease, both this substance and the metal it contains may sooner or later prove themselves new industrial agents in the hands of man. It remains only to discuss the most advantageous method of extracting vanadic acid, and it will be seen that the operation may be reduced to a very simple process :

M. Beauvallet, M. Pisani, and myself began by boiling the baked clay of the flower-pots with three per cent. of its weight of carbonate of soda and a sufficient quantity of water. Finding that caustic soda, as recommended by H. Deville, appeared to answer better, I repeated the experiments with it in place of

the carbonate. The boiling must be continued for several hours, and even then the total extraction of the vanadic acid is not effected. The filtered liquid containing silica and alumina is neutralized with sulphuric acid, and then ammonia and sulphydrate of ammonia are added. The whole is left at rest for two hours to separate the silica and alumina; the filtered liquid contains sulpho-vanadate of ammonia, whence sulphovanadic acid is thrown down by excess of acetic acid and boil- · ing. We can also separate vanadic acid by adding chloride of ammonium in excess, boiling, filtering, and adding to the filtered liquid a solution of tannin, which causes a blue precipitate, nearly black, containing all the vanadium contained in the liquid. M. Deville calcines the material from which vanadie acid is to be extracted with a little caustic soda, and then submits the whole to lixiviation. The filtered alkaline solution is saturated with sulphuretted hydrogen, which precipitates the silica and alumina, whilst the vanadic acid remains in solution as sulpho-vanadate of soda. In these cases the sulpho-vanadic acid is transformed into vanadic acid by roasting. These processes are somewhat tedious, and do not appear to yield all the vanadic acid present in the substance experimented on.

The method I prefer is simply a modification of Seftsröm's original process. It is applicable to any mineral substance, and gives very satisfactory results.

About half an ounce of the mineral (iron ore, clay, etc.), finely pulverized, is intimately mixed with half its weight of saltpetre, and the mixture heated to a dull red heat for fifteen or twenty minutes in a platinum crucible. The residue is treated with boiling water, to which a small fragment of caustic soda is added; it is then boiled for about a quarter of an hour, filtered, and the residue washed with boiling water. The liquid is nearly saturated with nitric acid, and precipitated by excess of chloride of barium; the precipitate is decomposed by sulphuric acid, the filtered liquid neutralized by ammonia, and saturated with chloride of ammonium. The whole of the vanadic acid present comes down as vanadate of ammonia in the course of two days. In some instances the process may be rendered more simple still; and for extracting vanadic acid on the large scale from iron ores, pitchblend, or from London clay, it will be sufficient to calcine a given quantity of these substances with one-fourth to one-half of their weight of a mixture of carbonate of soda and nitrate of potash; the calcination lasting about half an hour. The calcined mass is then boiled for some time with a little water, the liquid filtered, and supersaturated with chloride of ammonium. If the filtered liquid is too bulky it must be evaporated. All the vanadic acid is precipitated as vanadate of ammonia in the course of twenty-four

to forty-eight hours. This salt being collected and dried, is submitted to a careful calcination in an open crucible, the temperature being kept moderate. The vanadic acid thus produced has clear chocolate colour, and is nearly chemically pure.

In thus preparing vanadic acid on a large scale, care should be taken to employ chloride of ammonium as pure as possible. If this salt contains chloride of iron (as is frequently the case), the vanadic acid obtained will have a reddish colour, which is not observed in the pure acid.

In conclusion, I will add that Berzélius discovered that when vanadate of ammonia or vanadate of potash is added to a decoction of gall-nuts, a very good writing ink is produced, which may be said to be almost indelible; also, that I have found that vanadic acid cannot be detected in mineral substances by the ordinary blow-pipe test when a certain quantity of titanic acid is present.

UTILIZATION OF THE MAIZE PLANT.

Ar the Great Exhibition of 1862 specimens of paper manufactured from the Indian corn or maize plant were exhibited, and in our number for July, 1861, we mentioned that paper of this description was used in Austria for the books required in the primary schools. The present price of cotton is most likely destined before long to experience a great fall; but it is still for the good of society that fibres of other kinds hitherto neglected should be made available for the multifarious manufactures which civilization requires. It is also highly important, in this as in other directions, to utilize waste products, as the average condition of mankind cannot be materially improved so long as considerable sources of wealth and comfort are thrown away. Applied science is continually engaged in obtaining beautiful and valuable results from materials which ignorance pronounced to be good for nothing, or positively mischievous; and as necessity sharpens the inventive faculties, the dearth of cotton may, in the end, give rise to so many new manufactures and processes as to take its place amongst those numerous instances of a temporary evil evolving a large amount of permanent good.

Dr. Forbes Royle long ago pointed out a vast quantity of Indian fibre producing plants which were not utilized; but neither he nor any other scientific inquirers ever directed attention to the capacities of a vegetable body which appears better worth attention, than what is called, the refuse of the maize. Over large tracts of country in America, in Italy, in Hungary,

and elsewhere, Indian corn or maize constitutes the chief food of the population, and is produced in such abundance that the leaves and stalks can be obtained in immense quantities and at a low price. Attempts to utilize these portions of the maize plant are not altogether new, but Dr. Alois Ritter Auer von Welsbach comes before the public with what appears to be a complete scheme, and he has taken out patents for his inventions in the chief countries of the world. In a paper before us, he divides the products of maize refuse into three classes-fibrous, nutritious, and paper-pulp. He extracts from the leaves of the plant an organic substance, which he tells us resists putrefaction, and which we therefore conclude cannot be rich in the nitrogenous matters that constitute the chief value of the better kinds of food. It may, however, be good, as we are informed, to mix with flour, and it is stated to keep bread from getting, what is termed, dry-a condition which is more dependent upon molecular changes than upon actual loss of water by evaporation. We have not had an opportunity of seeing or tasting this material, but through the kindness of Martin Diosy, Esq., the Hungarian wine-merchant, in Fenchurch Street, we have received samples of the other articles which Dr. Welsbach's process affords. First, we have a handful of fibre like fine hemp; next, the same fibre spun into threads; thirdly, the threads woven into a strong coarse brown linen cloth, like fine sacking; fourthly, a strong, partially bleached cloth, of good whitey-brown colour, even texture, and considerable strength; fifthly, sixthly, and seventhly, we have finer and whiter qualities of the same kind of cloth, which the ladies of the household pronounce capable of being used for a variety of domestic purposes. After these, we find pulp for paper making, bleached and unbleached, and then comes a very interesting collection of paper of various kinds, some stiff and suited for drawing, some exquisitely transparent and firm, for tracing, others for writing and printing, some in the curious condition of parchment-paper, and others again delicate in texture, and of various ornamental tints.

It is no business of ours to go into commercial details; those who need them may be referred to M. Diosy or Dr. Welsbach; we look at the matter merely in a scientific and technological point of view, and regard the series of products before us as a very interesting illustration of how many useful things may be made out of a neglected portion of the vegetable world.

The result of operations carried on at the Austrian Government mills, near Vienna, is reported to show that three to three and a-half hundred weight of maize leaves yield forty pounds of thread, sixty pounds of paper-pulp and thirty of flour. We have no details of the process of manufacture, but it is stated to be exceedingly simple. The economical value of the plan depends upon

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a variety of considerations; but where the maize is extensively grown, and there are local facilities for manufacture and transport, it would seem well worth the consideration of practical men. As the seed of the plant sells for sufficient to give a profit on the cost of cultivation in suitable localities, and as three useful substances, amounting in the aggregate to 130 lbs. out of three hundred weight of leaves, can be extracted, there is ground to hope that the process may pay. The pecuniary consideration is, however, foreign to our objects, and if we had fully studied them, we should decline offering an opinion. All that belongs to us to say, is, that Dr. Welsbach has displayed considerable technological skill in producing the series of objects that have been sent for our examination, and we hope his labours will be of value in creating a new branch of industry, and augmenting the supply of materials in daily and increasing demand.

FURTHER NOTE ON THE COAL SUPPLY.

BY PROFESSOR ANSTED, F.R.S.

My attention has been drawn to an error more unaccountable than really important, in reference to the argument in my article on the "Supply and Waste of Coal," in your last number. I have said, in page 322, that an acre of land contains 2840 square yards. I need not remark that the real figure is 4840; but what was originally, probably, a slip of the pen, I have inadvertently carried out in a little calculation with reference to the quantity of coal in each square mile, one foot thick; and again in the estimated grand total of coal under certain probabilities (p. 323), and the available remainder, in page 325. I can no more account for the error than in the case of a mistaken date; but the reader may observe that the value of the argument is really unaffected. I had no intention to do more than give a general illustration, and it matters little whether the actual quantity of coal left is estimated at thirty-five or sixty-five thousands of millions of tons, the present consumption being a hundred millions, and rapidly increasing.

The figures should be as follows:

:

Each square mile of coal, one foot thick, contains 968,000 tons, and if the mean thickness is fifty feet, and the area 6000 square miles, the quantity is 290,400 millions of tons. The fourth part of this available is 72,600 millions, and the remainder 65,000 millions. This would be exhausted in a few centuries, under the supposed conditions, and economy is therefore loudly called for.

I must apologise to your readers for an error that certainly ought not to have been allowed, but of which Ican giveno account.