Fatty Foods, Their Practical Examination; A Handbook for the Use of Analytical and Technical Chemists (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. General Analytical Methods. It is unfortunate!)7 too often assumed that the analysis of fatty materials is of a rough and ready character, but it cannot be too clearly understood that the utmost possible precision, not only of the analytical procedure, but also in the preparation and standardisation of the reagents and instruments employed, is absolutely necessary in such analysis. For this reason all burettes, pipettes and measuring vessels of any kind should be carefully checked by the analyst under the conditions of his own work, though on account of the difficulty of checking instruments of large capacity, it is advisable to obtain these certified, either at the National Physical Laboratory or at Charlottenburg, and to bring all other apparatus into line with these by actual weighing. (1 c.c. = 0-99807 grm. weighed with brass weights in air at 60 F.). Similarly in the case of the standardisation of solutions, such standardisation should be carried out against solutions of the same normality. For instance N/10 acid should be standardised against N/10 alkali directly made up, and not against a solution made by diluting the normal strength ten times, and so on. The necessity of these precautions will be understood when we consider the high molecular weights involved in fat analysis. In these days of yearly publication of revised atomic weights, care must be taken to employthe same figures for all purposes. For instance, in calculating nitrogen, analysts invariably employ 14 as the atomic weight of nitrogen, but will at the same time calculate N/H2SO4 as containing 49 grm, per litre (instead of 49-04). Preparation of Sample for Analysis. Case 1: Fat Or On, per se.?The sample must (if necessary) be brought into the liquid condition at the lowest possible...