[Histonet] pH of formalin

Tony Henwood (SCHN) tony.henwood at health.nsw.gov.au
Wed Jun 6 20:52:49 CDT 2018

We routinely use the following

Hew-Shue (1991) has described a useful pH indicator for working neutral buffered formalin solutions. Bromocresol purple (CAS: 115-40-2) , when added to formalin solutions, serves as an indicator of pH as well as, from a safety aspect, labelling the solution as formalin making redundant the dangerous "smell" test. At an acidic pH (5.2) the indicator colour is yellow whereas at pH 6.8, the colour is purple.

A saturated solution of the dye (about 0.2g/100mls) is prepared and 2 to 4 drops are added to 10 litres of neutral buffered formalin.

Hew-Shue N (1991) "Bromcresol Purple as a Colored Marker and pH Indicator for Ten Percent Neutral Buffered Forrnalin" J Histotechnol 14(4):257-260.

Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC), FFSc(RCPA) 
Principal Scientist, the Children's Hospital at Westmead
Adjunct Fellow, School of Medicine, University of Western Sydney 
Tel: 612 9845 3306 
Fax: 612 9845 3318 
Pathology Department
the children's hospital at westmead
Cnr Hawkesbury Road and Hainsworth Street, Westmead
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA 

-----Original Message-----
From: Baldwin, Kathy via Histonet [mailto:histonet at lists.utsouthwestern.edu] 
Sent: Thursday, 7 June 2018 4:09 AM
To: 'histonet at lists.utsouthwestern.edu'
Subject: [Histonet] pH of formalin

Hi Histonetters
Is anyone out there monitoring their Ph of the formalin they use?  If do how often?

S Kathy Baldwin ASCP, SCT
Pathology and Cytology Manager
Ph 812-996-0210
Fax 812-996-0232

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