Mixed indicator papers

Solution A Pipet 2.0 mL of Standard Lead Solution (20 pig of Pb) into a 50-mL color-comparison tube, and add water to make 25 mL. Adjust the pH to between 3.0 and 4.0 (using short-range pH indicator paper) by adding 1 N acetic acid or 6 N ammonia, dilute to 40 mL with water, and mix. 

Add 1 drop of methyl violet indicator solution and introduce dilute HC1 or dilute NH3 solution (as necessary) dropwise and with constant stirring until the colour of the solution is yellow-green a blue-green colour is almost but not quite acid enough, yet it is acceptable for most analyses. (If the indicator paper is available, the thoroughly stirred solution should be spotted on fresh portions of the paper.) It is recommended that a comparison solution containing, say, 10 ml of 0-3m HC1 and 1 drop of indicator be freshly prepared this will facilitate the correct adjustment of the acidity. A more satisfactory standard is a buffer solution prepared by mixing 5 ml of m sodium acetate, 5 ml of 2m HC1, and 5 ml of water this has a pH of 0-5. 

A cold process with solid caustic soda or austic potash allows an accurate approach at home. The following parts by weight can be used for 10 parts solid austic soda, or 14 parts austic potash, dissolved in 20 parts hot water 72 parts beef tallow OR 73 parts lard OR 75 parts olive oil OR 71 parts palm oil. Gendy melt the fat, if solid. The two liquids are best mixed at around 40 C, mixing too warm or at uneven tempertures are common errors. Pour the fat then the caustic soda into a suitable vessel and stir or shake vigorously. Mixed well the two liquids should not separate, if they do they must be reshaken or stirred. After a week the soap can be tested to see if it produces suds. Test for excess alkalinity with indicator paper. 

Hydrochloric acid, HCl, (1 1), 25 mL/S Mixed indicator. Methylene blue Methyl red, pH change 5.4 (base form - green acid form - lavender) pH indicator paper, wide range, 10 cm/S... 

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