Re: chemicals and price


Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Tue, 18 May 1999 08:28:20 -0400


> "karl.holzhauser" wrote:
> ... Now, there are some different kinds
> of each chemical, some are cheeper than the other. They are called
> puriss, Analyse, purpurum... Is it neccesary, to buy the most
> expensive, or is the cheeper one as good as the other for our
> use.

I use analyzed reagent grade as I wish to know what is in there if a
problem does occur. Also when a particular chemical runs out and more
is purchased, there is far more consistency using the reagent grade. I
do not mind the additional price because I feel the consistency and
piece of mind as to what it contains is worth it.

However, the most inexpensive will probably work fine if tested
properly. The less expensive versions of a chemical product generally
have more impurities. These impurities may or may not adversely affect
the process in which the chemical is used (most often they will not).
For example: muriatic acid for etching concrete is a fine version of
Hydrochloric acid (usually 20% HCl), but the swimming pool version
contains additives that I have found troublesome. I prefer analyzed
reagent grade (and I use phosphoric acid) because it has been certified
as to the low amount of iron in it. If there is an abundant amount of
iron (which could come from the unfiltered tap water as well), it will
not clear the iron materials from the print as well. And worse if the
amount of iron varies, it could alter the clearing times, times which
have already been tested. Another example: table salt can be used for
NaCl (Sodium Chloride) however some of these contain non-soluble
particles, particles which might cause problems. Sea salt contains
particles of manganese which could remain as specks in the print.

My suggestion is that any lower grade chemicals should be substituted
and tested only one at a time. And whenever a different batch of that
lower grade chemical is used , it be tested as well. If one has a
process which gives them "good" prints, then the materials are probably
OK. If one has difficulties with a process, it is very hard to know
what has happened if several of the materials are lower grade and have
not been tested to be OK.

Part of that piece of mind I pay for is knowing that I have used top
grade chemicals and the problem (if there is one) is most likely related
to something else. Paper, I test new batches of paper; ambient
conditions, I regulate best I can and make notes; tap water, I filter to
0.5 micron; procedure, I am very consistent; Oh nuts, I sneezed.

Any cook can make soup; the master chef uses the finest ingredients.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/



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