76

fully exhausted of air before the water in c reaches the zero of the scale; in that case the level of the water in the tubes D and c will not be the same, but will be higher in D; it is evident, however, that this slight defect can be at once remedied by momentarily unfastening the spring clamp at q.

The apparatus should be placed so as to be out of reach of direct sunlight, and should also be protected against artificial heat, and all sources of heat which might give rise to sudden changes of temperature; the instrument is best placed near a north window, so as to afford sufficient light for reading off the height of the water in the tubes. The following reagents are required for use with this apparatus:

Hydrochloric Acid.-The acid required for the decomposition of the bone-black is poured into the vessel s

for use during experiments. This acid need not be pure; the crude acid of commerce answers the purpose, provided it be so diluted that its specific gravity at 17° C. is 1.120. It is not even necessary to adhere rigorously to this strength, and for all purposes here required, it is sufficient to mix two parts by bulk of water with one part by bulk of the commercial hydrochloric acid.

Carbonate of Ammonia.-In order to prepare the solu tion of this salt of the necessary strength, one part by weight of the ordinary carbonate of ammonia of the shops is dissolved in four parts of water, to which one part of liquid ammonia has been added. The salt is first coarsely pulverised, and immediately after placed in a bottle provided with a well ground-in glass stopper; there is next

CHEMICAL NEWS, Aug. 12, 1870.

Preliminary Operations. It is of the greatest importance that a good average sample, really representing the entire bulk of charcoal, be taken for investigation; this can be readily obtained by taking, say, from the filter (in sugar works) or from a cask, small samples, say a few ounces, at various depths of the vessels containing the material; or, better still, if there be room, the charcoal should be placed in a heap on a large sheet of stout canvass, and well mixed together, and samples taken from various spots of the heap. These, if wet (as will be the case with charcoal just removed from the filters), should be dried by suitable means, and afterwards the whole sample should be coarsely ground and thoroughly mixed, and a portion thereof taken for the purpose of being ground up to a very finely divided powder, to serve the purpose of weighing a sample from. It is essential that the charcoal should be ground to a very fine powder, because it greatly promotes the decomposition in the apparatus by the acid.

Weighing off of the Sample for Analysis.-We have seen that there is added to the apparatus a metallic weight to serve as normal weight. This weight is placed in one of the pans of balance (when no balance is at hand purposely made for chemical weighing, any balance, provided it be sensitive to from 1-8th to 1-10th of a grain, will answer the purpose); in the other pan a small porcelain basin is placed, and equilibrium is restored by means of small lead shot. As soon as the equilibrium is restored, the normal, or standard, weight is removed from the pan of the balance, and there is placed in the small porcelain capsule and added to the pan as much of the sample of bone-black to be tested as is required to restore the equilibrium. When several experiments have to be made consecutively, it is better to arrange beforehand the joint tare weight of the normal weight, and of a watch glass of suitable size, and to weigh off upon the latter the several samples. The author recommends the transference of these weighed quantities to a porcelain capsule, because, according to his plan, the samples, after having been weighed, have to be thoroughly moistened with the solution of carbonate of ammonia already referred to, in order to convert any caustic lime which might happen to be present in the material into carbonate of lime; but we think it is a decided improvement to moisten gently with the aforesaid solution of carbonate of ammonia a sufficient quantity of the samples to be tested previous to weighing them; to dry these, as also directed by Dr. Schiebler, and to apply at last, for a few moments, a stronger heat short of red heat (say an air or fusible metal bath, heated to 240° C.), so as to obviate the chance of either an excess of carbonate of ammonia or of water being present, while, at the same time, the decomposition of the carbonate of lime is guarded against. After the samples are quite cold, they are to be transferred to the flask or bottle A. The author states that more recent researches have proved that bone-black which has been once used for filtering purposes in sugar works no longer contains any caustic lime, and the treatment with carbonate of ammonia can therefore be dispensed with in that case, and need only be employed with samples freshly made.

The experiment for the quantitative estimation of the carbonic acid is carried out in the following manner :First the water in the tube c is made to stand exactly at the zero (0) of the scale; next the weighed sample of the bone-black to be tested is transferred with great care and without loss, to the bottom of the bottle, A, which should be perfectly dry inside and quite clean. This having been

NEWS

done, the gutta-percha vessel, s, which should also be previously well cleaned, is filled with the hydrochloric acid above referred to, to within from to inch from the top, care being taken not to drop any hydrochloric acid on the outside of that vessel; this gutta-percha vessel is next placed within the bottle A in a slanting direction, as shown in the woodcut; after this the glass stopper is replaced on A, care being taken to slightly grease it and the inside of the neck of A, thereby securing a better air-tight fitting. The closing of A will (if all parts of the apparatus are properly tight) have the effect of slightly lowering the level of the water in c, below the zero of the scale, while the water will rise just as much higher in D; by unfastening, for a moment, the spring clamp at q, the normal height is properly restored. The operator should very carefully guard against handling or touching A after it has been once closed, because, by so doing, the warmth of his hand will cause the expansion of the air in A, and thereby affect the proper action of the apparatus. In order to cause the hydrochloric acid contained in the guttapercha vessel placed inside A to run on to the animal charcoal, placed on the bottom of A, as described, the flask or bottle A is taken hold of by the neck, as delineated in the woodcut. As soon as the acid comes into contact with the bone-black, the evolution of carbonic acid gas begins, and with it also the expansion of the very thin india-rubber bladder, K, while the water in the tube c sinks, and correspondingly rises in While the bottle A is held in the right hand, as already indicated, and gently moved about so as to promote, as much as possible, the contact between the acid and the charcoal, the left hand is employed to gently open the spring clamp, p, in such a manner as to run off towards E just as much water as is required to keep the level in the tubes C and D at the same height; both these manipulations should be continued as long as any sinking of the level of the water in c is perceptible; in other other words, as long as any carbonic acid is given off. After this has quite ceased, and no change is perceptible, or any motion of the water in the tubes, just alluded to, has taken place, the operation may be considered at an end, care being taken, however, to keep the levels in the tubes c and D at precisely the same height. This having been done, the next step is to read off the height of the water at the scale on c, and simultaneously the thermometer.

D.

into the pump; and ƒ represents the tube through which the water is fed to the pump.

NEWS, vol. xix., p. 160), I find no small difficulty in In the pump described by Bunsen, Fig. 1 (CHEMICAL adjusting the end of the tube, p, so that the above conditions may be fulfilled. I have worked with four different pumps of this pattern, but have never obtained of flow. At times, when the rate of flow was small, a completely satisfactory result for all rates of speed collect just below the pump. a bubble or air space as much as a foot long would

I tried the form Fig. 2, in which the water flows through After experimenting for some time with the form Fig. 1, a tube of uniform bore throughout its entire length, and the air is drawn in through a small aperture in the side is attained very fairly, the tube being filled with the desired of the tube. By this arrangement the result sought for even mixture of bubbles of air and water. Fig. 3 represents a simpler form of the same apparatus, which affords equally good results, and which now receives preference to other forms in the laboratory of the Institute of Technology.

Some time after I had devised this form of pump, I observed that Sprengel (CHEMICAL NEWS, vol. xvii., P. 85) had previously described a similar tube to be used as an aspirator. It should be observed that Sprengel's aspirator is worked by pressure of a column of water, which has not yet entered the apparatus, while in Bunsen's arrangement the power is derived solely from the column of water which has passed the point at which the air and water mix.

The idea subsequently occurred to me that the bubbles might be delivered more evenly and of uniform size if the air were made to bubble up through water contained in a little reservoir, as in e, Fig. 4. I find, in fact, that in passing through the water in the reservoir, e, the air naturally breaks up into bubbles of uniform size and shape. The same result may be accomplished just as well by the somewhat simpler arrangement, Fig. 5, in which the enlargement, e, is dispensed with, but the position is main

tained.

The mode of working of this apparatus is probably as follows:-The feed water tends to flow up the air-tube, k (Fig. 5), but is met by the air which is being drawn in by the column of water in the waste-tube and is thus forced back for a moment so that a bubble of air is delivered into i; the water then rushes up again towards k, and is again forced to retreat so as to allow another

By ROBERT H. RICHARDS, M.E.

In the summer of 1869 I was asked by Professor Storer to put up Bunsen's filter pump for the laboratory of the school. In complying with his wishes I have been led to try a number of experiments upon the most efficient form of pump, and have arrived at some conclusions which seem to be worth recording.

It is evident, à priori, that an even flow of air and water is necessary, in order to obtain the best results, otherwise the tension of the air inside the partially exhausted vessel will not be constant. The bubbles of air should be round rather than elongated, should be uniformly distributed throughout the entire length of the column of water, and of no smaller diameter than the pipe itself, for if the bubbles are of less diameter than the pipe they will continually flow upwards through the water, and thus a portion of the useful effect of the water would be lost; and if the bubbles are much longer than the diameter of the tube, the vertical column of falling water may be much diminished in length.

In each of the figures (Figs. 1, 2, 3, 4, 5), a represents the air-tube, or the tube through which the air is drawn

* Communicated by the Author.

air and water evidently occurs at this point.

I have made several pumps of the form represented in Fig. 5, of tube varying in size from -inch bore to -inch, taking care that the air-feed and waste-tubes in each one of the several pumps should be, as nearly as possible, of the same, and I find that even the pump of -inch bore will yield bubbles of equal size and equally distributed when the supply of air is checked as would be the case when used to exhaust air from a vessel, or when the air is fed into the pump through a small orifice. In this form of apparatus, Fig. 5, the water has no tendency to flow down the walls of the tube, so as to leave elongated air spaces in the centre.

The great advantage of Figs. 3 and 5, is the ease with which they may be made, a single T-joint forms the whole essential part of the construction, but in Fig. I the end of the tube at p must be carefully adjusted, otherwise the water cannot be allowed to flow at a very slow rate. Fig. 3 will answer well for pumps -inch in bore or less, but the form. Fig. 5 should be used for any pump larger than -inch. Fig. 5 represents the only form of pump which, when of a bore much exceeding 1-inch, seems to be capable of taking down air in the form of bubbles; hence it is the form to be used, if this principle is ever applied on a manufacturing scale in chemical works, in procuring a vacuum for pumping mines, &c.

80

great number of dyers now prepare the colouring matter as they require it. It may, however, be precipitated by means of tannin or acetate of sodium, collected on filters and drained to a paste, and, if necessary, dried. In both these forms it is found in the market.

The aldehyd green is principally employed in silk dyeing. It is a splendid colour, and very brilliant both by day and artificial light. The chemistry of this green is at present hidden in obscurity, as it is very difficult to obtain in a chemically pure condition. But like the colouring matter previously described, it is undoubtedly the salt of an organic base apparently containing sulphur.

This base is colourless, or nearly so, and becomes changed to the normal colour of aldehyd green upon absorption of carbonic acid.

It will also decompose ammonia salts, combining with the acid and becoming green. I have here a solution containing the colourless base of this green, an ammonia salt and a little free ammonia. If I pour it upon a piece of white blotting-paper it does not stain it, but if I heat it the ammonia salt is decomposed, and we get the green developed with its ordinary intensity.

There is another green of an entirely different nature to the aldehyd green; it is called the iodine green. This colouring matter is always produced, but in variable quantities, in the preparation of the Hofmann violets, from magenta and iodide of ethyl or methyl. Of late, much attention has been directed to this colouring matter, and by making a few alterations in the process for preparing the Hofmann, from forty to fifty per cent of product can now be obtained from the magenta used. The iodine green is much used for cotton and silk dyeing; its colour is bluer than that of aldehyd green, and it is, therefore, more useful, as it yields, with the addition of yellow, a greater variety of green shades.

Iodine green contains an organic base which is not precipitated by alkaline carbonates. With picric acid it forms a difficultly-soluble picrate, and is generally prepared on the Continent as a paste consisting of this colour precipitated with picric acid and drained on a filter. In England it is, however, sold in alcoholic solution. It is a good green by gaslight.

The next green I have to bring before you is a magenta derivative, commercially called "Perkin's green." In its properties it resembles more closely the iodine than the aldehyd green, but differs from this in its solubility, and in being precipitated by solutions of alkaline carbonates, as carbonate of sodium. It is an organic base which is nearly colourless, and is by no means a chemically powerful body. Like the iodine green, it is precipitated by picric acid, forming a picrate which crystallises from alcohol in small prisms with a golden reflection. This colouring matter is principally employed for calico printing, and is now extensively used. Thus you see we have three aniline greens, some useful for one, and some for another purpose, so that the silk and cotton dyer, and the calico-printer, as well as others can be supplied. For fastness these greens are, I think, quite as good as the violets; the aldehyd green, however, I believe, resists light the best.

In the formation of the mauve, or aniline purple, there is always a small quantity of a second colouring matter produced, of a rich crimson colour, similar to that of safflower. Several years ago I examined this substance, and found it to dye silk a remarkably clear colour, but owing to the press of other matters, and the very small quantities in which it could be obtained, I did not give it any further attention. By a new process, however, it can now be produced in somewhat larger quantities, and endeavours are being made to introduce it to the arts, as it produces beautiful tints of pink upon silk and cotton, and, moreover, can be used for printing cotton, silk, and wool processes, to which safflower cannot be applied as it will not bear steaming. This aniline pink or crimson is a beautiful chemical body, crystallising in small prisms, possessing a golden green lustre. It is soluble in alcohol,

CHEMICAL NEWS, Aug. 12, 1870.

and also in water; it produces solutions remarkable for their fluorescence, so much so, that by certain lights they appear as if filled with a precipitate. In colour and fastness it is equal to safflower, and should it be found possible to manufacture it at a moderate price, I should imagine it would entirely supersede that colouring matter, especially as it is not affected by alkaline solutions.

There is a product in the English market supposed to be an aniline colour called "Field's orange," after its discoverer, Mr. Frederick Field. Its properties are those of a nitro-acid, but as its preparation has not been described, of course I cannot tell you anything about it. With alkalies it forms a rich orange-coloured solution, but by the addition of an acid it is precipitated as a pale yellow powder.

Field's orange is a very useful colouring matter, having a great affinity for animal fibres, and is extensively used for wool-dyeing, as it resists the action of light very well. We now come to a colouring matter of a very indefinite nature. I refer to aniline black. This substance appears to be closely allied to the insoluble part of the black precipitate formed in the manufacture of the mauve. This precipitate, however, always contains oxide of chromium, which cannot exist in the aniline black generally employed, as no chromium compound is used in its preparation, but as copper compounds are used, it may be that aniline black represents the black precipitate with the oxide of chromium replaced by the oxide of copper, or it may even be that in either case the metallic oxide is not an essential part of this black substance.

Aniline black is perfectly insoluble, and has, therefore, to be formed upon the fibre when employed for calico printing. As we shall have to refer to its application to dyeing and printing, I will not make any further remarks upon it just now.

From mauve and magenta, chocolate maroons and browns are prepared, but, as they are of secondary importance as yet, I will only just mention one or two of the methods of preparing them.

One of the processes for preparing chocolate from magenta is by the action of nitrous acid, but care has to be taken to watch the progress of the operation, and to stop it when the required shade has been obtained. Another process consists in heating magenta with hydrochlorate of aniline to a temperature a little above 200° C. The product, when purified, produces a maroon colour. Browns are generally obtained from the residue of magenta making.

All the colouring matters we have considered up to the present time are derivatives of aniline and toluidine, and constitute nearly all the colours of the rainbow.

By the action of nascent hydrogen upon dinitrobenzol, Mr. A. H. Church and myself obtained, in 1857, a crimson colouring matter, which was named nitrosophenyline. I have lately made a few new experiments upon this remarkable body, and find that it has an affinity for pure cotton, dyeing it of a clear cerise colour, considerably less blue in tint than safflower. With very dilute acids, this colouring matter forms a blue solution; with less dilute acid, a crimson colour, and with concentrated sulphuric acid a green colour. It is difficult to judge of the probable utility of this colouring matter, as it is so difficult to obtain in quantity by the present process. I may mention that my new experiments with this substance have caused me to doubt the purity of the product examined by Mr. Church and myself; and this is not remarkable when we consider how few methods of purifying artificial colouring matters were known at the date of our experiments, as well as the small amount of substance at our disposal.

We now turn to a product very different from aniline, though related to it in some respects very closely. On the table you will see a coal-tar product called "phenol," or "carbolic acid." It was discovered, a long time since, by Runge, and afterwards studied by a great number of chemists. It is only, however, during the last few years, that it has been introduced into commerce in a pure con