Amjuneri?2iarm" }     Scientific  and  Technical  Abstracts.  449 
to  cyanosis,  and  patients  have  to  be  more  carefully  watched.  Anal- 
gesia by  Cotton's  ether  is  apparently  identical  with  primary  anaesthe- 
sia such  as  can  be  obtained  with  any  other  anaesthetic,  but  it  is  pos- 
sible with  the  new  ether  to  maintain  the  analgesic  state  for  a  much 
longer  time,  with  the  patient  fully  conscious  and  with  fairly  good 
control  of  all  voluntary  muscles.  (From  the  Prescribe}',  No.  176, 
194;  May,  1921.) 
Preparation  of  Pure  Carbon  Dionide. — Robert  Crosbie 
Farmer,  of  the  Royal  Arsenal.  Woolwich,  prepares  carbon  dioxide 
completely  free  from  air  by  the  reaction  between  potassium  hydro-, 
gen  carbonate  and  sulphuric  acid.  Carbon  dioxide  is  passed  through 
a  solution  of  potassium  hydrogen  carbonate  (300  grams  to  the  litre) 
and  also  through  a  solution  of  sulphuric  acid  (120  cc.  diluted  to  1 
litre)  ;  the  solutions  are  thus  rendered  free  from  dissolved  air;  they 
are  then  caused  to  react  in  an  air-free  vessel ;  and  pure  carbon  diox- 
ide, entirely  free  from  air,  is  obtained.  The  product  is  so  pure  that 
it  gives  practically  no  gaseous  residue  on  absorption  with  potassium 
hydroxide  solution.  {Journal  of  the  Chemical  Society,  1920,  cxvii, 
1446-1447;  through  Journ.  of  the  Franklin  Inst.,  Feb.,  1921.) 
A  Qualitative  Reaction  for  Magnesium. — F.  Eisenlohr  de- 
scribes the  following  test  for  magnesium.  An  alcoholic  solution  of: 
alkanet  root  is  prepared  and  to  5  cc.  of  it  is  added  a  drop  of  ammo- 
nium carbonate  solution  of  2N  strength.  This  produces  no  appreci- 
able change  of  color,  but  if  additions  are  made  of  a  few  drops  of 
neutral  solutions  of  either  magnesium,  barium,  calcium,  strontium  or 
manganous  salts  the  following  effects  are  respectively  produced : 
Magnesium      Barium      Calcium      Strontium      Manganese  (ous) 
blue  violet      no  change       blue         blue  violet  blue  violet 
The  colorations  produced  by  magnesium,  strontium  and  man- 
ganous salts  are  not  strikingly  different,  but  if  the  solution  is  acidi- 
fied with  not  more  than  two  drops  of  2N  hydrochloric  acid,  the 
liquid  changes  to  bright  red,  and  then,  if  again  rendered  alkaline  by 
a  like  volume  of  ammonium  carbonate  solution,  becomes,  in  the  pres- 
ence of  magnesium,  blue  violet.  In  dealing  with  an  ordinary  phos- 
phate precipitate,  this  is  dissolved  in  2X  hydrochloric  acid,  and  a 
