spec_density: Calculate specimen density

In nicholascarey/respfun: Collection of useful functions for respirometry data and experiments

Calculate specimen density

Description

Given a wet mass (wet_mass) and buoyant mass (buoy_mass), this function calculates the density of a specimen. Bouyant mass is the downward force exerted while the specimen is in water, typically measured by having a measuring plate within a tank of water suspended from a balance above the tank. For species such as molluscs this can be used to determine the ratio of shell to tissue mass. It can also be used to calculate a specimen volume for correcting the water volume of a respirometer (see eff_vol). The temperature (t) and salinity (S) at which the buoyant mass was determined are required (as is atmospheric pressure (P) which defaults to 1.013253 bar, if not otherwise specified).

Usage

spec_density(wet_mass = NULL, buoy_mass = NULL, t = NULL, S = NULL, P
  = 1.013253)

Arguments

wet_mass	numeric (kg). Wet mass of specimen.
buoy_mass	numeric (kg). Buoyant mass of specimen.
t	numeric (°C). Water temperature at which buoy_mass was determined.
S	numeric (ppt). Water salinity at which buoy_mass was determined.
P	numeric (bar). Atmospheric pressure at which buoy_mass was determined. Defaults to 1.013253.

Inputs

Inputs must be in SI units:

• wet_mass and buoy_mass in kg

• t in °C

• S in ppt

• P in bar (Defaults to 1.013253)

Positively buoyant specimens

The function should work with positively buoyant specimens (i.e. less dense than water). Given a bouyant weight measured as buoyancy (i.e. lift force on a balance while in water), this can be entered as a negative value for buoy_mass and the function should return the correct density value. However, none of this has been tested.

Output

Output is a single numeric value for the density in kg/m^3.

Author(s)

Nicholas Carey - [e-mail]

See Also

eff_vol

nicholascarey/respfun documentation built on June 15, 2025, 11:46 a.m.