The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks.
- James Lane-Notter
- Date:
- 1900
Licence: In copyright
Credit: The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks. Source: Wellcome Collection.
Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.
101/1146 page 79
![sample down to the tint given by the other : 60 c.c. of the 100 c.c. are taken and made np to 100 with distilled water : on comparison, suppose the colour to be still too deep : 70 c.c. of this diluted water is then taken and compared with the other. Presuming 60 70 that the colours or tints now coincide, we get ^ ^ T00~^^ °^ original 100 C.C. equal to 1 c.c. of the standard potassium nitrite solution, which again equals 0-046 mgm. of NO2: therefore Mii^^=a; = 0-085 mgm. NOg in 100 cdi, or 0-085 part per 100,000. Had the glass containing the 1 c.c. of standard sokition been the darker, that could have been diluted down in a similar way, and the various fractions calculated as jiarts of 1 c.c. or equivalents of 1 c.c. in terms of NO,. The reactions in this process consist in the conversion of the sulphanilic acid into diazo-henzene sulphonic anhydride, by the nitrites present: this compound is in turn then converted by the naphthylamine into azo-a-amido- naphthalene-parazobenzene sulphonic acid. It is this last named compound which gives the pink colour to the liquid. Thus, Sulphanilic Nitrous Diazo-benzene acid. acid. sulphonic acid. CgH^NSOa + HNOa = CgHjNaSOs + 'iHaO Uiazo-benzene -won^ifiivinmino Azo-alpha-amido-napthalene- sulphonic acid. J>apnonyiaraiiie. parazobenzene sulphonic acid. CeH^NaSOa+CioH^NHgCl = CioHe(NH2)NNC,iH4HS03 + HCl. It may be accepted as a good rule that no water ■which shows the presence of nitrites is fitted for domestic use. Determination of the Nitrates.—For this estimation we have two convenient processes, either of which can be readily performed: they are (1) the phenol-sulphuric acid method, and (2) the aluminium process. Phenol-Sulphuric Acid Method.—This method is simple in its applica- tion, and yields good results : for it the following solutions are required :— (1) Phenol-sulphuric acid, made by adding 6 grammes of jiure phenol and 3 c.c. of distilled water to 37 c.c. of strong sulphuric acid free from nitrates. (2) Standard solution of Potassium Nitrate, made by dissolving 0-722 gramme of recently fused nitrate of potassium in water, and the solution subsequently made up to a litre. One c.c. of this solution will contain O'i milligramme of nitrogen. Tlic process is thus performed: 10 c.c. of the water under examination and 10 c.c, of the standard potassium nitrate solution are evaporated separately just to dryness in two porcelain or platinum dishes. To each of the residues, 1 c.c. of the phenol-sulphuric acid is added and thoroughly juixed by means of a glass rod. If the water under examination contains a large amount of nitrates, the liquid will quickly turn red; if it contain but a small quantity, this colour will not appear for about ten minutes. After the di.shes have stood for from ten to fifteen minutes, their contents are wa.shed out successively with 25 c.c. of distilled water into two clean Xe.s.s]cr glasses, about 20 c.c. of liquor ammonia added (sp. gr. 096), and both made up to 100 c.c. with more distilled water. Any nitrate present in the solutions converts the phonol-sulj)hurie acid into i)icric acid, which, by tlic action of the ammonium, fonns ammonium I)icrate : this gives a yellow colour to the solution, the intensity of which is proportional to the amount present. The colours of the two solutions arc now compared, and the darker one diluted until tlie tints arc adjusted, the calculation being made as explained](https://iiif.wellcomecollection.org/image/b2135764x_0101.jp2/full/800%2C/0/default.jpg)
