Question for paraformaldehyde in PBS buffer

[Bob Niemhuis]

You need to heat the PBS to 60 degrees C, and then it will all
dissolve.

Bob

Andrew Huang wrote:
> 
> Dear Sir/Madam,
>         Do you ever prepared for 4% paraformaldehyde in PBS buffer?
> In immunohistochemical staining procedure, I found when I dissolved 4%
> paraformaldehyde in 0.1M PBS buffer, there will be lots of
> unsoluable, white materials in bottom. I'm so confused whether it is
> natural results or my procedure is wrong. Could anybody tell me how and
> why it is, please? Thank you!
> 
> Sincerely
> 
> Andrew