*Parts*
Pharmacopoeias
express some concentrations in terms of the number of 'parts' of solute
dissolved in a stated number of 'parts' of solution.

**Molarity :**Moles of solute per liter of solution.

[Example:
Molecular weight of NaOH is “40” (Na=23; O=16; H=1). When the unit of this
number is expressed as “gram” and when this 40 gm of NaOH is dissolved in 1
liter solution this is called “1 molar NaOH Solution”

**Molality :**Moles of solute per kilogram of solvent.

[Example:
Molecular weight of NaOH is “40” (Na=23; O=16; H=1). When the unit of this
number is expressed as “gram” and when this 40 gm of NaOH is dissolved in 1 kilogram
of solvent this is called “1 molal NaOH Solution”

**Normality :**Equivalent weight of solute per liter of solution.

[Example:
Molecular weight H

_{2}SO_{4}is “98” (and equivalent weight of H_{2}SO_{4 }is “46”. When the unit of this number is expressed as “gram” and when this 46 gm of H_{2}SO_{4}is dissolved in 1 liter solution this is called “1 normal H_{2}SO_{4}Solution”**Moles :**When the molecular weight of a compound expressed as mass and unit is “gram”, then this amount is called as mole of that compound.

*Mole fraction*
This is often
used in theoretical considerations and is defined as the number of moles of
solute divided by the total number of moles of solute and solvent, i.e.:

n

_{1}
mole fraction of
solute

*( x*= -----------_{1 })*n*

_{1}+ n

_{2}

where

*n\*and*n**2*are the numbers of moles of solute and solvent, respectively.

*Mill/equivalents and normal solutions*
The concentrations
of solutes in body fluids and in solutions
used as replacements for those fluids are usually expressed in terms of the
number of millimoles (1 millimole = one thousandth of a mole) in a litre of
solution. In the case of electrolytes, however, these concentrations may still
be expressed in terms of milliequivalents per litre. A milliequivalent (mEq) of
an ion is, in fact, one thousandth of the gram equivalent of the ion, which is
in turn the ionic weight expressed in grams divided by the valency of the ion.
Alternatively,

ionic weight in mg

1mEq =
----------------------------

valency

**Percent:**

One part per hundred is
generally represented by the percent (%) symbol and denotes one part per 100
parts, one part in 10

^{2}**ppm:**

One part per moillion (

**ppm**) denotes one part per 1,000,000 parts, one part in 10^{6}; One ppm is equivalent to 1 milligram of something per liter of water (mg/l) or 1 milligram of something per kilogram solid (mg/kg) (1/1,000,000)**ppb:**

One part per billion (ppb) denotes one part per
1,000,000,000 parts, one part in 10

^{9}, One ppb represents one microgram of something per liter of water (ug/l), or one microgram of something per kilogram of solid (ug/kg). (1/1,000,000,000)**ppt:**

One part pertrillion (

**ppt**) denotes one part per 1,000,000,000,000 parts, one part in 10^{12}
(1/1,000,000,000,000).

**ppq:**

One part per quadrillion (ppq) denotes one part per
1,000,000,000,000,000 parts, one part in 10

^{15 (}1/1,000,000,000,000,000).
gggggggggg

ReplyDeletethanks, Very useful information.

ReplyDeleteThe big confusion is clear now..

ReplyDelete