148 
Varieties. 
f  Am.  Jour.  Pharns 
t      Mar.,  1879. 
A  Novel  and  Simple  Method  of  Taking  Specific  Gravities. — M.  Gannal  has 
recently  devised  a  means  of  determining  exactly,  and  with  the  greatest  facility,  the 
specific  gravity  of  all  liquids. 
With  his  "  densimeter  hydrostatique  "  all  calculation  is  obviated,  and  the  specific 
gravity  is  ascertained  by  simply  reading  the  weight  on  the  balance. 
This  useful  and  ingenious  apparatus  is  made  in  the  form  of  an  oli<ve,  so  that 
bubbles  of  air  shall  not  attach  themselves  to  its  sides. 
The  olive  (whether  made  of  glass  or  metal)  has  a  volume  exactly  equal  to  one 
decimal  subdivision  of  a  cubic  meter.  There  are  two  different  methods  employed 
in  the  practical  use  of  the  apparatus : 
1st.  We  may  suspend  it  on  the  platform  of  the  balance,  and,  after  having  produced 
an  equilibrium,  we  plunge  it  into  the  liquid  ;  the  equilibrium  is  then  destroyed  by 
the  loss  of  weight  of  the  olive,  and  the  number  of  grams  which  it  is  necessary  to- 
add  to  the  scale-pan  to  restore  the  equilibrium,  is  the  exact  specific  gravity  of  the 
liquid. 
2d.  Or  we  may  equally  well  adopt  the  following  plan  :  We  put  the  liquid  whose 
specific  gravity  we  desire  to  ascertain  in  a  glass  vessel  on  one  pan  of  the  balance  5 
we  balance  the  scale-pans,  and  then  suspend  the  olive  in  the  liquid  by  means  of  a  fine 
thread.  The  equilibrium  is  destroyed,  and  the  scale  descends  on  the  side  on  which 
the  olive  is  suspended,  and  the  weight — which  it  is  necessary  to  place  in  the  other 
pan  to  restore  the  equilibrium — is  equal  to  the  specific  gravity  of  the  liquid. 
This  apparatus  will  determine  the  density  of  all  liquids,  whether  they  be  heavier 
or  lighter  than  water,  whether  they  be  acids,  alcoholic,  thick  or  syrupy.  It  advan- 
tageously supersedes  the  areometers ;  it  is  not  fragile,  and  it  gives  the  indications 
with  an  exactitude  depending  on  the  sensibility  of  the  balance  employed.  The  work 
is  reduced  to  a  simple  weighing  and  reading  of  the  weights  on  the  balance. 
M.  A.  Gannal  has  constructed  instruments  of  100  cubic  centimeters  and  10  cubic 
centimeters  only.  The  larger  apparatus  is  the  one  which  will  prove  the  most  con- 
venient and  the  most  needed  in  commercial  and  industrial  determinations.  With 
this  instrument  and  a  balance  sensitive  to  1  decigram,  we  may  determine  the  density 
to  the  thousandth  degree. — Jour,  Frank.  Inst.,  Dec,  1878,  from  Les  Mondes,  Sept. 
26,  1878. 
Pure  Salicylic  Acid  as  a  Preservative  of  Drinking  Water.— Hugo  Schiff  states 
that  0-3  parts  salicylic  acid,  added  to  1000  parts  of  drinking  water  containing  much 
organic  matter  and  kept  in  a  stoppered  bottle,  which  was  opened  from  time  to  time,, 
entirely  prevented  its  decomposition,  it  tasting  perfectly  fresh  at  the  expiration  of 
three  years.  Water  can  also  be  prevented  from  decomposing  by  adding  a  minute 
quantity  of  bisulphide  of  carbon  to  it,  or  of  phenol  in  salt  water,  hut  will  then  not 
be  fit  for  drinking. — Ber.  d.  deutscb.  Chem.  Ges.,  XI,  p.  1528. 
Preservation  of  Solutions  of  Gum,  Glue  and  Gelatin.— M.  Regensburg  recom- 
mends adding  to  1  liter  of  the  solution,  in  hot  rain-  or  distilled  water,  from  60  to 
80  drops  of  silicate  of  soda,  and  stirring  the  mixture  well  for  five  minutes.    If  the 
