Air, water, and food from a sanitary standpoint . illed water add 5 of a solution of gram of phenol-phthalein in 100 of 50 per cent, alcohol and add lime-water drop by drop until a slight permanent pink color isproduced. Add of the above calcium hydroxidesolution. The resulting solution is the standard lime-waterused for the tests. WATER ANALYSIS. For Ammonia.—Water Free from Ammonia.—The am-monia-free water used in this laboratory is made by redis-tilling distilled water from a solution of alkaline permangan- 255 256 APPENDIX B. ate in a steam-heated copper still. The
Air, water, and food from a sanitary standpoint . illed water add 5 of a solution of gram of phenol-phthalein in 100 of 50 per cent, alcohol and add lime-water drop by drop until a slight permanent pink color isproduced. Add of the above calcium hydroxidesolution. The resulting solution is the standard lime-waterused for the tests. WATER ANALYSIS. For Ammonia.—Water Free from Ammonia.—The am-monia-free water used in this laboratory is made by redis-tilling distilled water from a solution of alkaline permangan- 255 256 APPENDIX B. ate in a steam-heated copper still. The apparatus used isshown in Fig. 15. Only the middle portion of the distillateis collected. Oftentimes the distillate from a good spring-water may be used. Nesslers Reagent.—Dissolve grams KI in 250 water and add a cold solution of HgCl2 which hasbeen saturated by boiling an excess of the salt and allowingit to crystallize out. Add the HgCl2 cautiously until a slightpermanent red precipitate (Hgl2) appears. Dissolve this. Fig. 15.—Still for Ammonia-free Water. slight precipitate by adding gram powdered KI. Thenadd 150 grams of KOH dissolved in 250 of water. Makeup to the liter and allow it to stand overnight to settle. Thissolution should give the required color with ammonia withinfive minutes, and should not precipitate within two hours. Alkaline Permanganate.—Dissolve 233 grams of the beststick potash in 350 of distilled water. Filter this strong APPENDIX B. 257 solution, if necessary, through a layer of glass wool on a por-celain filter-plate. Dilute with 700 to 750 of distilledwater to a sp. gr. of , add 8 grams of potassium per-manganate crystals, and boil down to one liter to free thesolution from nitrogen. Each new lot of reagent must betested before being used, but when the chemicals used are allgood there should be no correction needed for ammonia inthe solution. Standard Ammonia Solution.—Dissolve
Size: 1805px × 1384px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectair, booksubjectfood
