Am.  Jour.  Pharra.  ) 
April,  1878.  J 
Liquefaction  of  Gases. 
Since  isomorphic  bodies  have  the  same  atomic  volume,  equivalent 
divided  by  density,  and  oxygen  belongs  to  the  group  of  sulphur,  the 
atomic  volume  of  which  is  ?22— ID>  according  to  Dumas  the  density  of 
solid,  and  probably  also  of  liquid  oxygen,  should  be  J  J=i .  Pictet  has 
verified  this  by  determining  that  a  tube  of  46*25  cc.  capacity  held 
45*467  grams  of  liquid  oxygen,  the  slight  difference  of  *8  gram  being 
probably  due  to  incomplete  filling  or  slight  variation  in  temperature. 
Cailletet's  Apparatus. — The  hollow  steel  cylinder  A  is  fastened 
to  an  iron  frame  by  the  straps  i?,  and  when  filled  with  water  through 
the  cup  G,  a  very  high  pressure  may  be  produced  in  any  vessel  with 
which  it  may  be  connected,  upon  turning  the  large  hand-wheel  M,  the 
hub  of  which,  revolving  in  the  journal-box  jP,  forms  a  nut,  by  which 
the  square-threaded  screw  of  a  steel  plunger  is  worked.  The  flow  of 
water  is  controlled  by  a  screw  plug  operated  by  the  small  hand-wheel 
O,  whereby  also  the  pressure  exerted  upon  gases  may  be  suddenly 
relieved.  The  water  is  forced  through  a  small  metal  tube  into  the 
hollow  cylinder  which  is  supported  by  the  tablet  />,  and  capable  of 
withstanding  a  pressure  of  900  to  1, 000  atmospheres,  measured  by  the 
