WASHING THE PRECIPITATE: A precipitate may be washed directly on the filter, or it may be washed partly by decantation and partly on the filter. If by decantation, the precipitate is allowed to settle, and the supernatant liquid is poured on the filter. Wash water is added to the precipitate, and after settling, the decantation is … Read more
After solution, certain minor operations may or may not be necessary, but as a rule the next essential operation is that of precipitation. In his qualitative work the student has already come across many cases of precipitation, and he will find that many of the methods there used are again applied for quantitative purposes. Silver, … Read more
When precipitation is complete the precipitate must be separated from the solution. The means of bringing about this separation will be described under this head. Under the next head (Washing) the completeness of this separation will be considered. Filtering Medium In quantitative gravimetric analysis the two materials generally used are paper and asbestos, and the … Read more
In the course of work completed, the problem so far met with has been the determination of the various elements (or compounds) present in a substance. In an ore, for instance, there may be present silica, iron, copper, arsenic, and sulphur, and it is the province of qualitative analysis to determine the presence or absence … Read more
Fire Assay Cupels: Calmix, Machine Made—Under the process of manufacture, the material used produces a cupel uniform in density and power of absorption with a firm and glossy surface that will not crack nor check. They embody the following advantages : Need no initial drying. Absorb more lead than bone ash. Greater absorbing power permits the … Read more
Colorimetric Assays Colorimetric Assays are assays in which the colour imparted to a solution by some compound of the metal to be determined is taken advantage of; the depth of colour depending on the quantity of metal present. They are generally used for the determination of such small quantities as are too minute to be weighed. … Read more