salinometer

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An instrument that uses electrical conductivity to measure the concentration of salt in a solution.

from The Century Dictionary.

• noun A form of hydrometer for measuring the amount of salt present in any given solution.
• noun A similar apparatus used for indicating the density of brine in the boilers of marine steam-engines, and thus showing when they should be cleansed by blowing off the deposit left by the salt water, which tends to injure the boilers as well as to diminish their evaporating power. Also called salt-gage.

from the GNU version of the Collaborative International Dictionary of English.

• noun A salimeter.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a salimeter

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a hydrometer that determines the concentration of salt solutions by measuring their density