Boiling stone

Diazomethane is easily decomposed by rough surfaces for this reason glass apparatus with scratches and also porous pot ( boiling stones ) should not be used. 

In the flask were succesively placed 0.10 mol of the sulfinate (note 2), 25 ml of dry, pure HMPT (note 3), 4 g of powdered sodium iodide, 40 g of zinc dust and some boiling stones. After swirling for a few seconds the flask was connected with the other parts of the distillation apparatus, the system was evacuated immediately by means of the water pump (note 4) and the flask was then heated cautiously (free flame). A vigorous reaction started suddenly and the cumulene and part of the HMPT passed over. When the distillation had stopped completely... 

To a mixture of 0.3 mol of the diol (see 111, Exp. 60) and 5 ml of pyridine were added with swirling and cooling in a bath of -30°C 85 g of precooled (-30°C) thionyl chloride. The addition was carried out in 10-g portions over a period of 20 min. The cooling bath was then removed and the temperature of the mixture was allowed to rise to 25 or 30°C in 4 h (occasional cooling may be necessary). Some boiling stones were then added and the mixture was warmed at 40 c for 45 min in a water-pump vacuum. Subsequently, the mixture was vigorously shaken with 200 ml of ice water and 20 ml of pyridine. Three extractions with diethyl ether were carried out. The extracts were successively washed with 3 N HCl and water and... 

The cavities are filled with the crystal water of the zeolite, which can be driven off by heating the name zeolite means boiling stone. In the empty cavities of the dehydrated molecular sieve other molecules can now be included, provided that their effective cross-section is not larger than the pore diameter of the zeolite. 

Balance, Analytical PM 2000, Mettler Balance, top loading, Mettler Boiling stones, Hengar... 

Deaerated water is prepared as follows. A boiling stone is added to distilled water which is then boiled under reflux for at least 5 minutes it is cooled in ice to room temperature under an atmosphere of oxygen-free nitrogen. 

Suddenly — WOOSH Product all over the bench Instant failure. Next time you put a boiling stone in before you start. No bumping. But your instructor won t let you forget the time you did it your way. 

Don t let this happen to you. Use a brand new boiling stone every time you have to boil a liquid. A close up comparison between a boiling stone and the inner walls of a typical glass vessel reveals thousands of tiny nucleating points on the stone where vaporization can take place, in contrast to the smooth glass surface that can hide unsightly hot spots and lead to BUMPING, a massive instantaneous vaporization that will throw your product all over. 

CAUTION Introduction of a boiling stone into hot liquid may result in instant vaporization and loss of product. Remove the heat source, swirl the liquid to remove hot spots, then add the boiling stone. 

Used as directed, the boiling stone will relieve minor hot spots and prevent loss of product through bumping. So remember. .. whenever you boil, wherever you boil,... 

Say you place 50 ml of liquid A (B.P. 50°C) and 50 ml of liquid B (B.P. 100°C) in 250 ml R.B. flask. You drop in a boiling stone, fit the flask in a distillation setup, and turn on the heat. Bubbling starts and soon droplets form on the thermometer bulb. The temperature shoots up from room temperature to about 35°C, and a liquid condenses and drips into the receiver. That s bad. The temperature should be close to 50 °C. This low-boiling material is the forerun of a distillation, and you won t want to keep it. 

Always use a boiling stone, but never add a stone to any hot substance or you will wear the hot substance. 

The thermometer can be replaced with an inlet tube. If your flask has the provisions for both a thermometer and an inlet tube, then by all means also leave the thermometer in the reaction. The inlet tube should always be used to prevent the bad bumping that goes along with vacuum distillations. Boiling stones are useless. 

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