In a message dated 9/29/00 8:07:15 AM Pacific Daylight Time,
[log in to unmask] writes:

<< In terms of cupric chloride
 bath chemistry, a comparison of the operating parameters between ORP and
turbidimetric
 methods of control is as follows:

            Method of Control                ORP                Turbidimetric

                  Cu (total), g/L             150-180                  210-235
                    HCl, N                        1 - 3
0.02-0.04
                    Baume'                      29 - 31
38-40
  >>

WRONG WRONG AND WRONG!
You can control the etchant to ANY READING in a ORP/acid/Baume' type
controller.  That is the beauty of that sort of system, versus the
turbidimetric system, the turbidimetric system defines what your readings
MUST be, whereas the other system allows you to choose what YOU want.

It is the replenisher  chemistry that really affects what Baume' you can run,
with Chlorate limiting you to lower levels of Copper, than Hydrogen Peroxide.

Rudy Sedlak
RD Chemical Company

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