Manual of basic techniques for a health laboratory - libdoc.who.int

Annex. Reagents and their preparation 363PVA powder and PVA fixative solutions are available from several commercialsources. There are many grades of PVA powder on the market, but the grades withhigh hydrolysis and low or medium viscosity are most satisfactory for preparingPVA fixative.PVA fixative working solution1. Heat a water-bath (or large beaker of water) to 70–75°C. Adjust the heat tomaintain this temperature range.2. Place the loosely stoppered flask containing the PVA mixture in the water-bathfor about 10 minutes, swirling frequently.3. When the PVA powder appears to be mostly dissolved, pour in the modifiedSchaudinn fixative solution, restopper and swirl to mix.4. Continue to swirl the mixture in the water-bath for 2–3 minutes to dissolve theremainder of the PVA, to allow bubbles to escape, and to clear the solution.5. Remove the flask from the water-bath and allow it to cool. Store the PVA fixativein a screw-cap or glass-stoppered bottle. Label the bottle “PVA FIXATIVE” andwrite the date. The fixative will keep for 6–12 months.Potassium hydroxide, 200 g/l (20%) solution (No. 45)Potassium hydroxide (KOH) pellets20gDistilled waterq.s. 100mlLabel the volumetric flask “POTASSIUM HYDROXIDE 20% SOLUTION” andwrite the date.Warning: Potassium hydroxide is corrosive.Potassium permanganate, 40g/l (4%) solution (No. 46)Potassium permanganate (KMnO 4)40gDistilled waterq.s. 1000mlDissolve the potassium permanganate in 300ml of distilled water in a 1000-mlvolumetric flask. Make up the volume to 1000ml with distilled water. Label thevolumetric flask “POTASSIUM PERMANGANATE 4% SOLUTION” and writethe date.Safranine solution (No. 47)1. Prepare a stock solution:Safranine O 2.5gEthanol (CH 3CH 2OH), 95%q.s. 100mlMix until all the safranine has dissolved. Transfer the solution to a glass-stopperedbottle. Label the bottle “SAFRANINE STOCK SOLUTION” and write the date.2. Prepare a working solution in a glass-stoppered bottle:Stock solution10mlDistilled water90mlLabel the bottle “SAFRANINE WORKING SOLUTION” and write the date.Store in the dark.Saponin, 10g/l (1%) solution (No. 48)SaponinSodium chloride (NaCl), 8.5g/l (8.5%) solution (No. 53)1 g100ml