Weighing Practices

The difficulties of working with small quantities of liquids are much greater than with small quantities of solids. For example a competent worker can, and does in fact, often work with 100 mg, of solid without any special apparatus. With liquids this is often not practicable because of the much greater losses entailed, particularly when it is realised that one ordinary-sized drop weighs about 50-100 mg. The account which follows gives details of modifications of standard apparatus suitable for the semi-micro scale defined above. 

Method 1. From ammonium chloroplatinate. Place 3 0 g. of ammonium chloroplatinate and 30 g. of A.R. sodium nitrate (1) in Pyrex beaker or porcelain casserole and heat gently at first until the rapid evolution of gas slackens, and then more strongly until a temperature of about 300° is reached. This operation occupies about 15 minutes, and there is no spattering. Maintain the fluid mass at 500-530° for 30 minutes, and allow the mixture to cool. Treat the sohd mass with 50 ml. of water. The brown precipitate of platinum oxide (PtOj.HjO) settles to the bottom. Wash it once or twice by decantation, filter througha hardened filter paper on a Gooch crucible, and wash on the filter until practically free from nitrates. Stop the washing process immediately the precipitate tends to become colloidal (2) traces of sodium nitrate do not affect the efficiency of the catalyst. Dry the oxide in a desiccator, and weigh out portions of the dried material as required. 

Dissolve 200 g. of sodium nitrite in 400 ml. of water in a 2-litre beaker provided with an efficient mechanical stirrer, and add 40 g. of copper powder (either the precipitated powder or copper bronze which has been washed with a little ether). Suspend the fluoborate in about 200 ml. of water and add it slowly to the well-stirred mixture. Add 4-5 ml. of ether from time to time to break the froth. The reaction is complete when all the diazonium compound has been added. Transfer the mixture to a large flask and steam distil until no more solid passes over (about 5 litres of distillate). Filter off" the crystalline solid in the steam distillate and dry upon filter paper in the air this o-dinitrobenzene (very pale yellow crystals) has m.p. 116° (t.c., is practically pure) and weighs 29 g. It may be recrystallised from alcohol the recrystallised solid melts at 116-5°. 

In the practical applications of Raney nickel it is more convenient to measure the catalyst than to weigh it. The product, prepared as above, contains about 0-6 g. of the catalyst per millilitre of settled material a level teaspoonful is about 3 g. of nickel. 

Elements that the researcher evaluates about competitors include plants, processes, raw material costs and avakabiHty, distribution channels, product development skills, service faciHties, personnel, pricing poHcies, eg, does the competitor lead or foUow , and practices or concessions to secure and hold large customers. AH of these factors are weighed and then the researcher decides on a strategy for the company. 

Rubber Industry Advisory Committee - A New Practical Guide to Complying with COSHH in the Rubber Industry Dust Control in Powder Handling and Weighing Dust and Fume Control in Rubber Mixing and Milling Control of Solvents in the Rubber Industry... 

T he best way to determine the capture efficiency is to use the same com tamiHants that are encountered in practical applications. The usually mi known emission rate in Eq. (10.132) can be evaluated by the use of different models especially in the case of evaporation, or by weighing the waste material or by measuring the contaminant concentrations and airflow rates in all exhaust ducts in the space and using Eq. (10.131) to calculate... 

During the early 1990s, several methods were developed to interpret the results of LCA studies in terms of environmental impacts. Some methods were also developed to weigh various impacts against each other. In the early 1990s, the practicing number of LCA experts increased considerably. 

Hydrocyanic acid may be approximately estimated by dissolving 1 gram of oil in 5 c.c. of alcohol, and adding 50 c.c. of water. Then add ammonio-silver nitrate solution and shake well. Acidify slightly with nitric acid, and collect, wash, and dry the silver cyanide precipitated. Ignite and weigh the silver, 4 parts of which correspond to practically 1 of hydrocyanic acid. 

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