October 1, 1894.] 



KNOWLEDGE 



231 



for sucn dye-stuffs as will dye cotton without a mordant, 

 e.g., the dipheuyl derivatives — Congo red and the benzidine 

 dyes. 



Cellulose Thiociirhonate. — Certain theoretical views led 

 Messrs. Cross and Bevan to an examination of tlie action 

 of carbon bisulphide on the mercerized cotton, with results 

 which will probably have most important practical appli- 

 cations in the near future, and which have already formed 

 the subject of at least one patent. 



If the above-mentioned compound of cellulose and soda 

 be exposed to the action of the vapour of carbon bisulphide, 

 it is gradually converted into a yellowish mass which, when 

 placed in water, swells up, and finally dissolves to form a 

 solution of Cellulose tldocarhonate. 



This same solution may be more readily produced by 

 bringing together two parts of cellulose, one of caustic 

 soda, two of carbon bisulphide, and eight of water. 



From this solution the thiooarbonate may be precipitated 

 in a pure state by addition of alcohol or strong brine, after 

 which it may be redissolved in pure water to form a 

 colourless solution of great viscosity. Thus, a four per cent, 

 solution is as thick as treacle, while a bottle filled with 

 one containing eleven per cent, of the thiocarbonate may 

 be inverted for a considerable time without any risk of 

 loss. But its most important property is its power of 

 coagulation, which occurs spontaneously on standing for a 

 considerable period, or immediately on healing above GO', 

 or by addition of an acid. This coagulation is due to the 

 cellulose separating out in the pure state, forming a 

 gelatinous mass which gradually shrinks, but in such a 

 manner as to form an exact miniature of the interior shape 

 of the containing vessel; all the sulphur and alkali are 

 found in the liquid which separates from the shrunken 

 mass. The cellulose thus reproduced varies in consistency 

 according to the concentration of the original solution, but 

 is always perfectly homogeneous; thus, it may be obtained 

 in a form closely resembling the softer varieties of india- 

 rubber, or in one practically indistinguishable from horn, 

 and it is not merely in appearance that this latter resembles 

 horn but also in its consistency, for it is hard and tough 

 and perfectly adapted for turning. Finally, it is found to 

 possess the same increased affinity for dye-stuffs that is 

 exhibited by the original " mercerized " cotton. 



The importance of the discovery is manifest, especially 

 in view of the inevitably failing supplies of ivory, which 

 have already resulted in the success of the ebonite and 

 celluloid manufactures, over which it is clear that this 

 preparation possesses many and great advantages ; for 

 none of the materials required in its production are 

 expensive, audit is free both from the brittleness of ebonite 

 and th3 inflammability of celluloid, while the readiness 

 with which it can be obtained m any desired shape gives 

 it a still more marked superiority over either of these 

 products. 



SYMPATHETIC EXPLOSIONS. 



By C. A. Mitchell, B.A. Oxon. 



IN an explosion we have the sudden evolution of large 

 quantities of gas which meet with external resistance. 

 Thus, in the case of dynamite, the substance is 

 suddenly decomposed into gases, which meet with 

 the resistance offered by the surface of the earth 

 on the one side and with that opposed by the weight of the 

 atmosphere on the other. 



Explosive agents are roughly classified as "high" and 

 " low " explosives, the former term being usually applied to 

 those exploded by detonators and used as destructive agents 



rather than for the propulsion of projectiles. Nitro- 

 glycerine and gunpowder may be taken as representatives 

 of the two classes. 



Substances liable to explosion are, as it were, in a state 

 of unstable eijuilibrium, and often a slight cause is sufficient 

 to so disturb that equilibrium that a fresh arrangement of 

 the particles takes place — in other words, an explosion. 

 A somewhat analogous instance of instability is to be 

 noticed in the case of water cooled , slowly below its 

 freezing-point without solidifying, as occasionally happens 

 in bedroom jugs. When the jug is lifted the movement 

 destroys the equilibrium and the water suddenly becomes 

 ice. Prince Rupert's drops illustrate the same phenomenon. 

 These are small pear-shaped globules prepared by allowing 

 molten glass to fall from a short distance into cold water, 

 which causes the exterior to cool more rapidly than the 

 interior, and the mass is left in such a state of tension that, 

 if the extreme tip of the drop he broken off with pliers, the 

 whole flies to powder. 



Explosive bodies differ very considerably in stability. 

 The so-called iodide of nitrogen, a black po'ft'der formed by 

 digesting iodine in a solution of ammonia, explodes when 

 dry with the slightest touch. Nitro-glycerine is more 

 stable and requires the blow of a hammer for its explosion. 

 This substance is prepared by allowing strong nitric and 

 sulphuric acids to act upon glycerine, care being taken to 

 keep the temperature low. It is an oily liquid and is 

 very poisonous. As an explosive it is uncertain and has 

 been the cause of many accidents. When mixed, 

 however, with an inert substance, such as sawdust, it is 

 much more stable. This is the principle made use of in 

 the manufacture of dynamite, which consists of nitro- 

 glycerine absorbed by a porous siliceous earth called 

 kieselguhr. 



Dynamite is very stable under ordinary conditions, as 

 was well shown in the experiments carried out in the 

 Lauenburg Fabrik in 1870." A barrel containing five 

 hundred and forty kilograms! was dropped a distance of 

 twenty feet on to a paved road, and in a second experiment 

 a weight of ten kilograms was dropped on to a dynamite 

 cartridge. In neither instance was there any explosion. 

 The dynamite used burned quietly when thrown on a fire, 

 but exploded powerfully even on an open surface when a 

 detonating cartridge was exploded in contact with it. We 

 have thus the curious phenomenon of a substance which 

 burns quietly and withstands a heavy blow, but which 

 disintegrates readily when another less stable body is 

 exploded beside it. This is explained by the theory of an 

 explosive wave which is communicated from the one 

 explosive to the other. Where an explosive burns quietly 

 there is much slower decomposition, and the particles 

 first taking fire radiate their heat too quickly for the 

 entire mass to be simultaneously raised to the temperature 

 of explosion. If the heat cannot be dissipated sufficiently 

 fast, as in the case of confined gun-cotton, an explosion 

 follows just as when a detonator is used. Thus the 

 unstable equilibrium may be disturbed either by heat or by 

 communication of a mechanical vibration. This latter 

 method of sympathetic explosion, as it has been termed, is 

 now very generally used to effect explosion of charges of 

 dynamite and gun-cotton. 



Thrt the deflagration of one substance can produce a 

 sympathetic explosion at a distance has baen illustrated 

 by many accidents. The explosion of a quantity of nitro- 

 glycerine in one shed has often caused the explosion of 

 other materials some distance away. A remarkable 

 instance occurred in 1888, in a factory at Wandsworth, 



» Ber. Deitt. Chem. Ges., IX., 1802. t A kilogram = 22 Iba. 



