Hi,
    It has been said that 1:1 is a mixture of equal parts. AND it has
also
been
said that concentrations are always given as part to whole. My point is
that
there is NO convention that is agreed upon by everyone. (And what's the
point of
a convention that is not agreed upon)
    It makes sense that as a titer goes down 1:100 ... 1:50 ... 1:10 ...

1:5 ...
1:2  that the conventions that go with this method should follow. If a
person
wants to describe a solution as a ratio then they should say "prepare
this
in a
1:2 RATIO".
    I do like one of the suggestions to use a different notation for the

different methods: 1/2 as one part in two and hence 1/1000 is one part
in
one
thousand. While 1:1 is the ratio one part to one part.
    The idea of always using percent dilutions has merit until you try
to
apply
this to immunohistochemistry. S100 diluted 1:1600 (part to whole) would
be
0.000625%. try making that up without a flinch ;-).
    Unfortunately, Who is going to follow these standards? Manufacturers

of
antibodies will still refer to their optimal dilutions as 1:400 and mean

part to
whole. I brought this up merely to emphasize that when we give
concentrations it
may be a good idea to specify what you mean.
    Our CAM5.2 is diluted one part in five (1:5). Weigarts Iron
Hematoxylin is
made by mixing equal parts of solution A and solution B (1:1). So a tech

having
just left a special stain and preparing to make an antibody dilution is
more apt
to get confused at these low titers.
    Just something to think about. Maybe someday there will be a
convention but
until then be careful.
Amos Brooks