AmNov.?i88h6arm*}    Practical  Notes  from  Various  Sources.  533 
MgO.  Serullas  found,  on  the  other  hand,  that  the  anhydrous  salt 
was  fusible  at  red  heat  without  decomposition ;  while  Lowig  dis- 
covered on  distilling  the  aqueous  solution  that  HBr  was  given  oif. 
Another  consideration  in  favor  of  the  first  method  is  the  cost, 
which  is  one-half  less  than  when  prepared  by  direct  solution  of  the 
granulated  bromide.  The  impracticability  of  preparing  it  by  double 
decomposition  between  magnesium  sulphate  and  calcium  bromide 
may  here  be  mentioned  and  resides  in  the  difficulty  of  obtaining  a 
product  of  constant  strength,  through  the  variable  quantity  of  water  of 
crystallization  in  the  one,  and  absorbed  moisture  in  the  other.  The 
high  cost  of  metallic  magnesium  effectually  precludes  the  utilization 
of  direct  combination  of  the  elements. 
PRACTICAL  NOTES  FEOM  VARIOUS  SOURCES. 
By  the  Editor. 
Sodium  rhodanate  has  been  found  by  Dr.  Paschkis  (Schmidt's  Jahr- 
bucher,  April,  1886),  to  have  an  action  similar  to  that  of  strychnine, 
but  less  rapid,  producing  in  frogs  prolonged  tetanic  convulsions  with 
inhibition  of  the  respiratory  and  cardiac  movements.  Injected  into 
the  arteries  of  mammals,  a  marked  increase  in  the  blood  pressure  is 
produced. 
The  salt  referred  to  is  the  sulphocyanide,  sulphocyanate  or  thiocy- 
anate  of  sodium,  and  is  prepared  by  neutralizing  thiocyanic  acid  with 
sodium  carbonate,  evaporating  the  liquid  carefully  by  the  aid  of  a 
water  bath  or  over  sulphuric  acid,  and  recrystallizing  the  dry  residue 
from  alcohol.  The  salt  forms  white  or  colorless  rhombohedric  crys- 
tals, which  are  very  deliquescent  and  freely  soluble  in  water  and  in 
alcohol.  Its  composition  is  expressed  by  the  formula  NaSCN.  The  aque- 
ous solution  does  not  produce  any  precipitate  with  baryum  chloride ; 
it  imparts  to  ferric  salts  a  deep  blood-red  color  which  is  not  affected  by 
hydrochloric  acid,  but  disappears  on  the  addition  of  corrosive  subli- 
mate. 
Potassium  sidphocynate  is  more  generally  met  with  than  the  sodium 
salt,  and  may  probably  have  the  same,  or  at  least  an  analogous  action. 
As  early  as  1818,  A.  Vogel  {Schweigger 's  Journal,  xxiii),  called  at- 
tention to  the  poisonous  narcotic  effects  of  the  potassium  salt. 
Bromide  of  Arsenic  is  given  by  Dr.  Davis  to  diabetics  in  doses  of 
