Reeder

Calcon carboxylic acid [3-hydroxy-4-(2-hydroxy-4-sulfo-l-napbtbylazo)napbtbalene-2-carboxylic acid] [3737-95-9] M 428.4, m 300°, X,max 560nm, pKj 1.2, pK2 3.8, PK3 9.26, PK4 13.14. Purified through its p-toluidinium salt. The dye was dissolved in warm 20% aq MeOH and treated with p-toluidine to ppte the salt after cooling. Finally recrystd from hot water. [Itoh and Ueno Analyst (London) 95 583 1970.] Patton and Reeder (Anal Chem 28 1026 1956) indicator and complexes with Ca in presence of Mg and other metal ions. 

Reeder, E. and Sternbach, L.H. U.S. Patent 3,109,843 November 5,1963 assigned to Hoff-mann-LaRoche Inc. 

Patton and Reeder s indicator. The indicator is 2-hydroxy-l-(2-hydroxy-4-sulpho-l-naphthylazo)-3-naphthoic acid the name may be abbreviated to HHSNNA. Its main use is in the direct titration of calcium, particularly in the presence of magnesium. A sharp colour change from wine red to pure blue is obtained when calcium ions are titrated with EDTA at pH values between 12... 

The titration with EDTA, using solochrome black as indicator, will yield the calcium content of the sample (if no magnesium is present) or the total calcium and magnesium content if both metals are present. To determine the individual elements, calcium may be evaluated by titration using a suitable indicator, e.g., Patton and Reeder s indicator or calcon — see Sections 10.48 and 10.60, or by titration with EGTA using zincon as indicator — see Section 10.61. The difference between the two titrations is a measure of the magnesium content. 

Discussion. Patton and Reeder s indicator (HHSNNA), see Section 10.48, makes it possible to determine calcium in the presence of magnesium, and is... 

The calcium content may then be determined by titration wth EDTA using either Patton and Reeder s indicator or calcon (Section 10.60), or alternatively by titration with EGTA (see Section 10.61). 

Palladium, D. of as dimethylglyoximate. (g) 463 as nioximate, (g) 474 by EDTA, (ti) 329 Paper chromatography 229 see Thin layer chromatography Parallax errors due to, 85 Parallel determinations 132 Partial ionic equations 850, (T) 851 Partition chromatography 13. 217 Partition coefficient 162 Patton and Reeder s indicator 317, 328 Peptisation 419. 421... 

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