Triple salt

Triple \Tri"ple\, a. [L. triplus; tri- (see {Tri-}) + -plus, as
   in duplus double: cf. F. triple. See {Double}, and cf.
   {Treble}.]
   1. Consisting of three united; multiplied by three;
      threefold; as, a triple knot; a triple tie.
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            By thy triple shape as thou art seen. --Dryden.
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   2. Three times repeated; treble. See {Treble}.
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   3. One of three; third. [Obs.] --Shak.
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   {Triple crown}, the crown, or tiara, of the pope. See
      {Tiara}, 2.

   {Triple-expansion steam engine}, a compound steam engine in
      which the same steam performs work in three cylinders
      successively.

   {Triple measure} (Mus.), a measure of tree beats of which
      first only is accented.

   {Triple ratio} (Math.), a ratio which is equal to 3.

   {Triple salt} (Chem.), a salt containing three distinct basic
      atoms as radicals; thus, microcosmic salt is a triple
      salt.

   {Triple star} (Astron.), a system of three stars in close
      proximity.

   {Triple time} (Mus.), that time in which each measure is
      divided into three equal parts.

   {Triple valve}, in an automatic air brake for railroad cars,
      the valve under each car, by means of which the brake is
      controlled by a change of pressure in the air pipe leading
      from the locomotive.
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