Liquid Soil pH test kits, what in them?

Discussion in 'The Science Forum' started by wireless_barf, Jan 11, 2012.

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  1. I need to test a big area of my soil for pH. The meter i have isnt reliable, and i dont find the use of indicator papers reliable either for this. Ive ordered a liquid based test kit, but it only does 15 samples.

    Do any of you learned chaps know what the liquid/buffer power etc contained in these kits is? If i can find that out, then its almost certain i can get decent quantities of it at reasonable prices from a chemical supply house and save myself a few bob.

    Im presuming its an indicator liquid and a pH buffer powder
  2. You're really wanting to test the latest batch of peruvian marching powder aren't you?
  3. I dont think it will be litmus per se, ive a feeling its more likely to be one or other of the various 'universal' indicators.

    Actually, PA, its to help try and cure club root. Think my plots too small to be cost effective growing showbiz sherbert
  4. All it is is litmus powder either added to liquid (distilled water) or impregnated in paper. You can buy it in bulk Litmus powder

    You can buy it from any pharmaceutical supplier.
  5. I think ordinary Litmus solution has too wide a range to be accurate, ie pH 1-14. For soil use it only needs to be between pH 5-8. The test kits all seem to give a green indication scale.

    Ive discovered that the powder in the kit is barium sulphate, which is a flocculant. Its there to clarify the sample suspension to make the indicator colour more readily visible.

    Nitrazine seems to have the required pH range, but im not sure how it indicates, i dont think ive ever had call to use it.
  6. With Nitrazine the color changes as pH changes, giving a broad range of colors from yellow through blue. Nitrazine strips are commonly used to test the vaginal pH of expectant mothers. :thumright:
  7. This the ph colour indicators for Nitrazine

  8. Thats the colour the kits give! So, Nitrazine it is. Wonder if i can convince the local midwife to bung me a few packets. Owt to be a tight twat