Niiro-Glvcerime Explosives. 95 



I shall reter lo them in some detail when the views are on the 

 screen, but now I need only say that these processes involve : — 



1. The separation of the nitro-glycerine from the acids. 



2. The separation of the acids from the nitroglycerine. 



3. The purification of the nitro-glycerine. 



4. The recoverv of the waste acids, and many others of lesser 

 importance. 



Nitro-gl\cerine is a heavy oil} liquid tjf r6 S.G.. having as a 

 rule a straw yellow colour, but when made from perfectly bleached 

 glvcerine and nitric acid, it is almost water white. It freezes about 

 i2°C., and the sp.gr. of the frozen body rises to i"735 (Guttmann). 

 This peculiaritv of freezing has led to more accidents in Europe 

 than all other causes combined. Ff)rlunalely. we do not often see 

 frozen nitro-glycerine explosives in South Africa. It has a slight 

 vapour tension, and a peculiar smell, \obel informed me some 

 years agi> before his death, that he had at one time distilled 1 cwt. 

 of nitro-glycerine under reduced pressure, which merely illustrates- 

 the fearlessness of the man. If perfectly purified and freed from 

 acids it .vill keep for an indefinite period, and I have seen samples- 

 20 years old. On the other hand, it sometimes takes it into its head 

 to decompose for no apparent cause, but I am convinced that in 

 every case this is the result of faulty manufacture. It is not neces- 

 sary to say anything about its sensitiveness to shock, as in general 

 terms this fact is fairly well known. 



When decomposed in a confined space it is resolved into- 

 carbonic acid, water, nitrogen, and oxygen, according to the follow- 

 ing equation : — 



2 C,,H, (XO.jsO, = 6C0, + 5H2O + bX + O. 

 so that it has in itself more than sufficient oxygen to burn up all the 

 elementary constituents. This is a most important point. Every 

 litre of nitro-glycerine equivalent to i"6 kilos by weight produce 

 1,141 litres of gas, a truly enormous quantity, the volume being 

 reckoned at 0°C and 760 m. pressure. The water is akso calculated 

 as in the gaseous state. The theoretical temperature at explosion 

 is 698o°C., and as the mechanical work is the function of the gas 

 volume by the temperature, one can readily realise how it is that 

 nothing else approaches it in power. The pressure exerted at the 

 theoretical temperature is 20,000 kilos per sq. centimetre, or,, 

 roughly, about 1,300 tons per .sq. inch. Taking equivalent volumes^ 

 of black powder and nitro-glycerine, the latter produces an explosion,, 

 a pres.sure 10 to 12 times as great as ordinary black ])owder, and 

 the actual work calculated weight for weight is roughU as three 

 to one. 



I have said quite enough about nitro-glvcerine to show vou — - 

 as indeed requires no demonstration— the enormous pote.itial 

 energy it possesses. I am almost tempted at this point to discuss 

 some matters which relate more to the domain of theory and 

 scientific research, but time does not permit, and I shall therefore 

 continue to look at the subject from its everydav practical aspect. 



I have referred incidentally to two nitro-glycerine explosives 



