A 3%-7% solution of HCl works good, Watch Citric, It can be difficult to rinse and forms Copper citrate crystals fairly easily. As for titrating a weak acid , use .01 n NaOH , take 1 ml of solution dilute to 50ml . titrate to ph 7 it should take about 10 ml of reagent , if not vary the ratio of working bath to water . KOH will also work in much the same way ---------- From: WHATEVER To: [log in to unmask] Subject: [TN] Acid stoper in developing Date: Wednesday, July 22, 1998 5:31AM I wonder how many of you using acid stoper during developing of dry film? say citric acid. and I would like to hear your comments. For those chemists out there, I like to know whether it is really possible to titrate a weak acid with three Ka ? Oh, by the way, anyone using resist lamintor with two sets of rollers, hot to hot; Like to try or modify a one, if you have some information, would you please share with me? Thanks. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################