EN Solution analysis

A. Assuming your reducer is sodium hypophosphite (you forgot to say) you will sample 5 mL from bath, use glass stoppered flask, add 5 mL concentrated sulfuric acid, add 50 mL 0.1N iodine solution, mix and place in dark for 30 minutes, add approximately 10 mL starch solution and titrate with 0.1N

(Na2S2O3) from almost black (very dark blue) to colorless endpoint.

Calculate your hypophosphite
(NaH2PO2.H2O) = (50mL (Iodine volume) x 0.1 (Normality of iodine) - mL consumed of titrant x 0.1 (Normality titrant)) x 1.413.
This will be in oz /gal x 7.82 gives g/L.

A. I Agree with the above hypophosphite analysis as for the Nickel analysis:

10 ml sample of ENP solution at room temperature
add 10 mls of ammonia ⇦ this on eBay or Amazon [affil links] buffer (water, conc. ammonia, ammonium sulphate ⇦ this on eBay or Amazon [affil links] )
100 mls water
Use murexide [affil links] as an indicator and titrate with EDTA from a light brown to pink/purple end point.

A. I would substitute the conc. sulfuric Acid for 50% strength or less and add a bit more to compensate (say 15 - 20ml). You're only adding the acid to liberate excess Iodine, which then reacts with the sodium thiosulphate ⇦ this on eBay or Amazon [affil links] (hence the name back titration). Adding conc. sulfuric Acid to such a small amount of sample, then pouring Iodine on top of this is a recipe for disaster, and could cause a nasty accident

A. 1. Yes, the endpoint is determined by the change in temperature of the solution.

thermometric titration

2. Yes, thermometric titrations do need special equipment for the most accurate, precise results. Automated thermometric titration systems employ the second derivative of the digitally smoothed temperature curve. You can find more information about the subject under the search item "thermometric titration" in Wikipedia. I think more competitors would increase the profile and utility of this valuable technique.

3. Yes, I have performed many thousands of thermometric titrations, including acid/base (aqueous and non-aqueous), redox, precipitation and complexometric approaches. It is fundamentally a superior technique to potentiometric titrimetry.