[Spacenova]

I have to standardisation perchloric acid (0,1 M). Blank measurement is necessary at standardisation?
The procedure is:
Add 0,35 g potassium hydrogen phtalate and 50 ml acetic acid glacial. Titrate with 0,1 M perchloric acid. 

[Arkcon]

This question isn't complete enough for a good answer.  Anyone on these forums can click your name Spacenova:, and they can see your previous postings that you do this quite often. I don't know why you do this, but you have to ask more complete questions to get a good answer.

[Arkcon]

Briefly, you probably should perform a blank, and use it in the standardization calculation, and the result calculation.  It may also depend on where you got your method from, and to what sort of quality standards (government or otherwise) your results are held to.  Perhaps, if you've purchased the 0.1 M perchloric acid, as a standard, from a company that verifies it as a volumetric standard, then you may use it as is, for a little while.  But this really all up to you, your group, your company, and the people auditing your quality results.  Putting it another way:  why not take a blank, report it, use it in the calculation, and submit it for review?