Processing, weighing

A Procedurefor the Specijication, Calibration and Testing of Strain Gage Eoad Cells for Industrial Process Weighing and Force Measurement, Institute of Measurement and Control, London. 

Process Weigh the crucible and cover as in Exp. 15, and weigh in the crucible about 1.5 gm. of dry, powdered potassium chlorate. Weigh to a centigram the exact amount taken, and record the weights thus —... 

Process Weigh accurately a clean, dry crucible. Weigh in it from 1.5 to 2 gm. of barium chloride, weighing exactly the amount taken. Record the results thus —... 

As explained in Sect. 29.1.2 for preparation processes weighing is generally preferred to volume measurements, because a better accuracy and precision can be obtained. 

A Guide to the Specification and Procurement of Industrial Process Weighing Systems, The Institute of Measurement and Control, 1999. 

Then again remove T, and drop a weighed pellet of the solute through the side arm A. Stir the mixture until a clear solution is obtained, and then repeat the above process until three consistent readings of the freezing point of the solution have been obtained. Then add a second weighed pellet of the solute, and determine the freezing-p>oint of this more concentrated solution in the same way. 

Wait a few minutes after the pellet has completely dissolved, and then continue taking readings as before until three consistent values are obtained. A second weighed pellet may then be added if desired, and the process repeated. 

Weigh out accurately about 2 g. of glycine, transfer to a 250 ml. graduated flask, dissolve in distilled water, make up to the mark, and mix well. Transfer 25 ml. of the solution to a conical flask, add 2 drops of phenolphthalein, and then again add dilute sodium hydroxide very carefully until the solution is just faintly pink. No v add about 10 ml. (/. ., an excess) of the neutralised formaldehyde solution the pink colour of the phenolphthalein disappears immediately and the solution becomes markedly acid. Titrate with AI io sodium hydroxide solution until the pink colour is just restored. Repeat the process with at least two further quantities of 25 ml. of the glycine solution in order to obtain consistent readings. 

The whole process is then repeated exactly as described above. The absorption tubes are then weighed and attached to the apparatus ffull details will be given below when a complete combustion is described), and the above process repeated. The absorption tubes are detached and reweighed. They should not have gained in weight by more than o i... 

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. 

Weighing is the operation of determining the mass of any material as represented by one or more objects or by a quantity of bulk material. Proportioning is the control, by weighing, of relative quantities of two or more ingredients according to a specific recipe in order to make a mixed product, or to prepare the ingredients for use in a chemical process. 

Tank and hopper scales weigh Hquids or bulk materials. The materials may be stored in the scale, or may be weighed while being transported for sale or for use in a process. The scale is usually part of a much larger material handling system. Capacities are mostly under 20 t, but can be as large as 200 t or more. 

Process industries frequently need to weigh and control the flow rate of bulk material for optimum performance of such devices as grinders or pulverizers, or for controlling additives, eg, to water suppHes. A scale can be installed in a belt conveyor, or a short belt feeder can be mounted on a platform scale. Either can be equipped with controls to maintain the feed rate within limits by controlling the operation of the device feeding the material to the conveyor. Direct mass measurement with a nuclear scale can also be used to measure and control such a continuous stream of material. 

---