Bumping boiling chip

R,5)-lbuprofen acid (20 g, 96.9 mmol), p-toluenesulfonic acid (0.44 g, 2.27 mmol) and 2-ethoxyethanol (21.9 mL, 224 mmol) were dissolved in the organic solvent, isooctane (180 mL). The boiling chips were added into the reaction flask as anti-bumping agent. Then the reaction mixtures were refluxed for 8—9 h using a Dean-Stark apparatus. 

It is highly advisable to distill both amines in the presence of boiling chips, otherwise bumping causes a serious problem it sets in vigorously and suddenly at the boiling point of the amine and may cause a large portion of material to be carried over mechanically into the receiver.]... 

The distillation must be carried out slowly enough (one drop per one to two seconds) so that the vapor will not be superheated. Superheating leads to decreased efficiency of separation and also to erroneous temperature indications. The bulb of the thermometer must be low enough to be completely bathed in vapors. In order to prevent superheating of the liquid and the bumping which results from this, it is advisable to add a few chips of porous plate or the commercial microporous boiling chips. ... 

Use boiling chips in the water bath so the water does not superheat causing bumping and possible breakage. 

The bottom collector is held in place by two small springs. The extract is placed in the flask, and the Snyder column attached. The apparatus is placed in a steam bath, so that the collector is in the steam and hot water. If the solvent boils at a low temperature, do not increase the heat at a later time or it may bump vigorously and come apart. If you add fresh solvent to wash the Snyder column, add a fresh boiling chip. The boiling chip is not a problem later on. The solvent is evaporated to very near dryness, and then any solvent desired is added by a microliter syringe to the volume desired. 

Add 4 to 5 porcelain boiling chips to the flask. (NOTE Do not add boiling chips to a hot solution later on). Boiling chips produce a stream of air bubbles when they are heated, which reduces the possibility of the solution "bumping". 

Add 4-5 boiling chips to the liquid in the r.b. flask to prevent bumping. 

In no case should a liquid be boiled without the addition of a boiling aid. Bumping is stopped by adding to the liquid a source of bubble nuclei, such as a boiling chip, a platinum wire, or an ebullition tube. Boiling chips are most commonly used. They are small chips of clean hard porous plate or tile about 2 to 5 mm in diameter. The small pores induce smooth boiling. Platinum wire acts as a porous material supposedly because of dissolved gas. 

As an additional precaution for the very delicate CB determinations a nitrogen gas flow of 10 mL/min through the condenser should be maintained during extraction. The flask is then cooled to approximately 0 °C, preferably in a freezer, before the solvent is removed by rotary evaporation at 0.1 hPa. TTie boiling chips stay in the flask, because removal is a potential source of contamination. At the low temperature of the solvent they will not induce boiling. A layer of ice growing on the outside of the flask retards the evaporation of the solvent (boiling point 76 °C at atmospheric pressure). It may be removed by immersion in a water-bath at 30 °C after 15 min. It is important to allow for this delay as aqueous acetonitrile tends to bump or boil explosively. 

---