Mdseagnite.  A  hydrous  ammonium  sulphate;  in  mealy  crusts,  of  a
yellow ish-grajr  or  lemon-yellow  color;  translucent;  taste  pungent  and
Ditter;  composition  (NHaWS  +  H2O  =  Sulphur  tiioxide  53*3,  am-
monia 22*8,  water  23*9  ;  easily  soluble  in  water.  Etna ;  Vesuvius ;
the  Lipari  Islands;  the  Guafiape  Isles,  in  guano.  One  of  the  products
from  the  combustion  of  anthracite  coal.
Lecontite.  Hydrous  ammonium  sodium  sulphate.  Near  Comay-
agua,  Central  America.
Bousstngaultite,  hydrous  ammonium -magnesium  sulphate.  Tus-
cany. Hannayite  is  another,  in  triclinic  crj^stals,  from  guano  in
Victoria,  with  struvite.
Struvite.  Hydrous  ammonium-magnesium  phosphate;  in  yellowish
crystals,  slightly  soluble  in  water.  Found  on  the  site  of  an  old  church
in  Hamburg,  where  there  had  been  quantities  of  cattle  dung.
TscTiet^migite.  An  ammonia  alum.  Tschermig,  Bohemia ;  Utah
Co.,  Utah.
La/rderellite.  A  white,  tasteless,  ammonium  borate.  Tuscan  la-
goons.
Hydrous  ammonium  pTiosphate  and  Ammonium  bicarbonate  {Tesche-
ma^cherite)  have  been  detected  in  guano;  also,  Hydrous  sodium-am-
monium phosphate,  called  Stercorite.
Oryptohalite,    A  probable  ammonium  fluosilicate.    Vesuvius.
HYDROGEN — WATER.  251


HYDROGEN.
Hydrogen  is  the  basic  constituent  in  hydrochloric  acid,
and  in  water.
Hydrochloric  Acid. — Muriatic  Acid,  Hydrogen  Chloride.
A  gas,  consisting  of  Chlorine  97'26,  hydrogen  2*74  =  100
=  HCl.     It  has  a  pungent  odor,  and  is  acrid  to  the  skin.
Rapidly  dissolved  by  water.  Passed  into  a  solution  of
nitrate  of  silver,  it  produces  a  white  precipitate  (silver
chloride)  which  soon  blackens  on  exposure.  Passes  off
whenever  common  salt  is  acted  on  by  sulphuric  acid;  occa-
sionally formed  about  volcanoes.
Hydrofluorite.  Hydrofluoric  acid  or  hydrogen  fluoride.  An  ema-
nation at  some  eruptions  of  Vesuvius,  as  observed  by  Scacchi.
WATER.
