CHEMISTRY. 



105 



the exterior; in the interior is a carefully- 

 turned brass box, slightly smaller than the 

 glas tube, and tinned to protect it from the 

 action of the ozone. Through this box a cur- 

 rent of ice-cold water can be passed, so as to 

 prevent the heating of the apparatus, the oxy- 

 gen or air passing through the annular space 

 between the box and the glass tube, which is 

 fitted with caps and tubes for that purpose. 

 The brass box and tin-foil coating are con- 

 nected with the induction coil in the usual 

 way. This apparatus yields large quantities 

 of ozone with great ease, and, with the same 

 battery power, appears to be more powerful 

 than either of the other forms of apparatus ; 

 its cost, moreover, is small, and it is not liable 

 to be broken. It can also easily be adapted to 

 other pieces of apparatus, and the current of 

 cold water keeps the apparatus cool, thus al- 

 lowing it to be used for any length of time." 



Oat- Manufacture. Ruck's process for gas- 

 manufacture, now being tested in London, is 

 thus described by Prof. Crookes, F. R. S. : The 

 apparatus consists of three iron gas-retorts set 

 in a single furnace, one over the other two. 

 Close above the retorts, and heated to bright 

 redness by the same fire, is a horizontal U- 

 shaped iron pipe, about four inches diameter. 

 The retorts are charged with a mixture of coke 

 and iron, and steam from an ordinary boiler is 

 then forced through the iron pipe, which, it is 

 obvious, acts as a superheater. The super- 

 heated steam passes into the two lower re- 

 torts, being carried by pipes arranged in their 

 axes to the farther end, and then returning 

 through the mass of heated coke and iron. It 

 then traverses the third retort in the same 

 manner, and in this way a large volume of gas 

 is generated, which is cooled in a temporary 

 condenser and carried to a gas-holder. It is 

 then purified in the ordinary way. The gas 

 so obtained has of course no illuminating, 

 though a very considerable heating value. It 

 is, in fact, a mixture of hydrogen, carbonic 

 oxide, and carbonic acid, the latter amounting, 

 it is said, to about 12 per cent. To render it 

 lutniniferous it is passed through a chamber 

 containing rectified petroleum-spirit of sp. gr. 

 0.68. A considerable quantity of the vapor 

 of this spirit is taken up, and the volume of 

 the gas is increased by about 25 per cent. The 

 gas then burns with a brilliant flame, and is 

 ready for distribution. 



Neither the decomposing nor the carbnret- 

 ting process is novel ; but the great question 

 is whether the product will fulfill all the re- 

 quirements of an illuminating gas to be carried 

 through the streets of cities under various con- 

 ditions of temperature, etc. It is of importance 

 to know whether and how far its illuminat- 

 ing power will stand the test of cold. Would 

 its vapor condense in cold weather, and, if so, 

 would the amount of this condensation be suf- 

 ficient to impair in any degree the valne of 

 the gas? The experiment witnessed by the 

 writer did not throw any light on this point. 



Some doubt also hangs over another matter. 

 The printed reports of the company claim for 

 the gas a specific gravity less than that of air ; 

 but, if it be true that it contains 20 per cent, 

 of liquid hydrocarbons, it is difficult to see 

 how this can be so. 



Indigo Dyeing and Printing. Messrs. Schn- 

 tzenberger and De Lalande have introduced a 

 new method of dyeing with indigo, which 

 possesses great advantages over all previous 

 methods. They find that indigo is almost in- 

 stantaneously converted into white indigo by 

 the action of hydrosulphite of soda. The 

 authors therefore substitute for the copperas 

 vat and the fermentation vat a hydrosulphite 

 vat, which they describe as follows : 



Bisulphite of soda, standing at 30 to 35 Baume, 

 is brought in contact in a covered vessel with twisted 

 sheet zinc or granulated zinc, filling up to the top of 

 the vessel without occupying more than one-fourth 

 of its real volume. After the lapse of about one hour 

 the liquid is poured into an excess of milk of lime, 

 which precipitates the salts of zinc. It is stirred, 

 and the clear liquid drawn off either by filtration 

 and pressure, or by decautation after the addition of 

 water. Air should be excluded as much as possible. 

 By mixing the hydrosulphite thus obtained with 

 ground indigo and the amounts of lime or soda need- 

 ful to dissolve the reduced indigo, we obtain at once 

 a yellowish liquid containing no insoluble matter 

 except the earthy impurities of the indigo. One 

 kilogramme of indigo may be thus reduced so as to 

 form a solution not exceeding 10 to 15 litres in vol- 

 ume. For dyeing, a certain quantity of the reduced 

 indigo solution is run into a vat filled with water. 

 This vat being clear in its entire dcpth-the operation 

 of dyeing involves no loss of time. The excess of 

 hydrosulphite constantly reduces the scum of oxi- 

 dized indigo forming on the surface of the dye-bath, 

 the strength of which can be kept up during working 

 by successive additions of the concentrated indigo 

 solution. Thus the required shade can be obtained 

 with the smallest possible number of dips. This 

 vat gives shades more solid and clear than can bo 

 obtained with the old vatSj and enables the dyer to 

 produce upon wool very light blue bottoms, which 

 are ordinarily got by means of sulphate of indigo, 

 and are in consequence much more fugitive. The 

 process at present employed for printing indigo-blues 

 consists in printing on white indigo, or indigo-talc 

 of tin, obtained by precipitating a tin vat with hy- 

 drochloric acid, or by adding to the clear portion of a 

 copperas vat a mixture of tin-salt and hydrochloric 

 acid. The precipitate, thickened with gum, is printed 

 on the calico, and then fixed with milk of lime. The 

 goods are next passed through a chloride-of-lime 

 bath, sulphuric acid, and soap. The process is diffi- 

 cult, delicate, and costly. Various attempts at im- 

 provement have hitherto failed in securing complete 

 success. We may mention as examples the faience 1 

 blue, pencil-blue, and printing with a concentrated 

 vat in an atmosphere of coal-gas, air being excluded. 

 The authors propose to print with an alkaline solu- 

 tion of reduced indigo, suitably concentrated and 

 thickened, containing a large excess of hydrosulphito 

 of soda. The presence of this salt tends to keep the 

 indigo-blue reduced, which otherwise tends to be- 

 come oxidized during the time of printing. This 

 part of the process can be carried out in common 

 air, and with an ordinary machine, the oxidation be- 

 ing so slight that after an hour's work the remnant 

 of the color in still yellow and soluble. By thus 

 printing on reduced indigo immediate fixation is se- 

 cured, and the entire coloring-matter is utilized. Ex- 

 perience has proved that, for equal shades, 50 to 60 

 per cent, less indigo is consumed with the new pro- 



