Micromeritics Elzone II 5390 Operator's Manual page 344

Elzone II 5390 Confirm
Wetting and dispersion are highly variable matters associated with the physical chemistry
of particle surfaces that can range from tens of square centimeters to hundreds of square
meters per gram. Nevertheless, only a few drops of a liquid dispersant or a few grains of a
solid one are needed. The dispersant preferably should be added directly to the sample and
the sample then added to the electrolyte. Ordinary household or laboratory detergents
very frequently are satisfactory. As a further source, however, Table D-1 lists commercial
detergents and some specific materials for which they have been found valuable.
When the particles are already in some effective electrolyte such as sea water, plating
solution, beer, crystallizer liquor, or when the particles are biological cells requiring iso-
tonic salinity (physiologically "normal" saline ) to avoid swelling, shrinkage, or other
damage, the choices become limited. In the first case, it probably will be necessary to
dilute with particle-free water. In the second case, the demand from hematology laborato-
ries has resulted in the ready availability of isotonic saline from laboratory supply houses.
Formulations vary slightly, but all include mono- and di-basic phosphate buffered to pH
7.4 with an osmolality of 335-345 m-osmos. Some are filtered down to 3 micrometers and
others to 1 micrometer.
Organic
Organic electrolytes are needed for water-soluble materials (including most salts and sug-
ars), many esters and foodstuffs, and for other materials already suspended in media that
are immiscible with water. For these, polar organic liquids having dielectric constants of
10 or more, with readily ionized compounds such as lithium chloride, ammonium thiocya-
nate, or ammonium perchlorate, form a useful group of electrolytes. Very useful organic
media include alcohols and ketones having from one to four carbon atoms. Amides and
esters are good for some samples. Often, when some other water-immiscible media is
involved, a polar liquid alone will not form a single liquid phase or the material may be
somewhat soluble in it. In these cases, chlorinated hydrocarbons, tetrahydrofuran, and ali-
phatic and aromatic hydrocarbons may be used for the suppression of particle solubility.
Be sure to handle organics carefully and in a well-ventilated area.
Adequate ventilation and handling precautions must be observed when working
with organic media.
D-2
Appendix D
5539-42822-01 (Rev A) - Nov 2017