Re: B5 Fixative & ? substitutes

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From:"J. A. Kiernan" <>
To:Histonet <>
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On Thu, 13 Jul 2000 wrote:

> Lori Karnes in Saskatoon, Saskatchewan asks about using Surgipath's I.B.F. 
> fixative as a substitute for B-5 fixative. 
> My information may be outdated, but in 1992 Surgipath described this fixative 
> as "an alcohol based tissue fixative that contains barium chloride and a very 
> low percentage of formalin." The barium chloride, which is (they claimed) not 
> a hazardous waste problem, was supposed to substitute for the mercury in B-5.

  Mercuric chloride fixes by coagulating proteins. The coagula are
  generally too small to see with light microscopy, unlike those
  from other coagulants like picric acid and alcohol. Barium chloride
  isn't a precipitant of proteins, so it could not substitute for 
  mercuric chloride in a fixative. 

  Barium salts are chemically similar to those of calcium, and may 
  help to maintain the integrity of some lipid structures. BaCl2 is 
  used in a mixture with formaldehyde in Saxena's silver method for
  showing the Golgi apparatus. Zinc chloride (or sulphate) is a
  protein precipitant that some people claim can replace mercuric
  chloride (see earlier HistoNet discussions), though perhaps
  not for every purpose. 

  Regarding toxicity, barium chloride is considered quite
  poisonous. Oral LD50 in rodents around 120 mg/kg. Mercuric
  chloride is about 10 times as toxic as this (Data from
  MSDS sheets). The nearest oral LD50 I can find for a zinc salt
  is 2460 mg/kg for zinc acetate (Merck Index). Zinc salts are 
  not considered dangerously poisonous. Barium chloride is a
  component of several traditional injection masses for
  showing blood vessels, ducts etc: it reacts with sulphate ions
  to give the completely insoluble (and harmless) sulphate - the
  same compound that is used in radiological examinations of 
  the GI tract.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1

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