I 
EMPLOYMENT  OF  NITROGLYCERINE  IN  QUARRIES.  525 
rapidly  under  the  form  of  a  heavy  oil,  which  is  collected  by  de- 
cantation  into  a  vessel ;  then  wash  it  with  a  little  water  which  is 
in  its  turn  decanted,  pour  the  nitroglycerine  into  bottles,  and  it 
is  ready  for  use. 
In  this  state,  the  nitroglycerine  is  still  slightly  acid  and 
watery ;  but  this  is  of  no  importance,  since,  as  it  is  employed 
soon  after  its  preparation,  these  impurities  in  no  degree  prevent 
detonation. 
II.  Properties  of  Nitroglycerine. — Nitroglycerine  is  a  yellow  or 
brownish  oil,  heavier  than  water  and  insoluble  in  it,  but  soluble 
in  ether,  alcohol,  &c. 
Exposed  to  a  prolonged  but  not  intense  amount  of  coldness,  it 
crystallizes  in  long  needles.  A  violent  shock  best  causes  it  to 
detonate.  The  handling  of  it  is  now  easy  and  only  slightly 
dangerous.  Spread  upon  the  ground  it  is  only  with  difficulty 
fired  by  a  body  in  combustion,  and  then  only  burns  partially ;  a 
flask  containing  nitroglycerine  may  be  broken  upon  stones  with- 
out its  detonating ;  it  may  be  volatilized  without  decomposition 
by  a  regulated  heat ;  but  if  it  boils,  detonation  becomes  immi- 
nent. 
A  drop  of  nitroglycerine  falling  on  a  metal  plate  moderately 
heated  volatilizes  quietly.  If  the  plate  be  red-hot,  the  drop  is 
immediately  fired  and  burns  like  a  grain  of  powder,  only  noise- 
lessly ;  but  if  the  plate,  without  being  red-hot,  is  hot  enough  to 
make  the  drop  boil  immediately,  it  decomposes  suddenly  with  a 
violent  detonation. 
Nitroglycerine,  especially  when  impure  and  acid,  decomposes 
spontaneously  after  a  certain  time,  with  an  escape  of  gas  and  the 
production  of  oxalic  and  glyceric  acid. 
Probably  the  spontaneous  explosions  of  nitroglycerine,  with 
whose  disastrous  effects  the  papers  have  acquainted  us,  are  owing 
to  the  same  cause.  The  nitroglycerine  being  enclosed  in  well- 
corked  bottles,  the  gases  produced  by  its  spontaneous  combustion 
cannot  escape ;  they  then  exercise  an  immense  pressure  on  the 
nitroglycerine,  and  in  this  state  the  least  shock  and  the  slightest 
movement  will  cause  an  explosion. 
The  flavor  of  nitroglycerine  is  at  once  sweet,  piquant,  and 
aromatic ;  it  is  poisonous,  and  taken  in  small  doses  it  produces 
