Spatula

When crystallisation is complete, the mixture of crystals and crude mother-liquor is filtered at the pump, again using a Buchner funnel and flask as described on p. 10, and the crystals remaining in the funnel are then pressed well down with a spatula whilst continual suction of the pump is applied, in order to drain the mother-liquor from the crystals as effectively as possible. If it has been found in the preliminary tests that the crystalline material is almost insoluble in the cold solvent, the crystals in the... 

Place 5 ml. of benzaldehyde in a wide-necked stout-walled bottle of about 100 ml. capacity (a conical flask is too fragile for this purpose) and add 50 ml. of concentrated dy 0 880) ammonia solution. Cork the bottle securely, shake vigorously, and then allow to stand for 24 hours, by which time the layer of benzaldehyde at the bottom of the bottle will have been converted into a hard mass of hydrobenzamide. (If after 24 hours the crude hydrobenzamide is still syrupy, shake the mixture vigorously and allow to stand for another hour, when the conversion will be complete.) Break up the solid pellet with a strong spatula, filter at the pump, wash with water and drain thoroughly. Recrystallise from ethanol methylated spirit should not be used, as it contains sufficient water to cause partial hydrolysis back to benzaldehyde and ammonia. Hydrobenzamide is obtained as colourless crystals, m.p. 101° (and not 110° as frequently quoted) yield, 4 g. 

Spatulas. Stainless steel, nickel and porcelain spatulas are available commercially. Some of these are shown in Fig. 11,1, 9 (a) is a spatula with a flexible stainless steel blade and is provided with a wooden handle (6) is a nickel spatula and has a tumed-up end to facilitate the handling... 

In order to dry the crystals, the Buchner funnel is inverted over two or three thicknesses of drying paper (i.e., coarse-grained, smooth surfaced Alter paper) resting upon a pad of newspaper, and the crystalline cake is removed with the aid of a clean spatula several sheets of drying paper are placed on top and the crystals are pressed flrmly. If the sheets become too soiled by the mother liquor absorbed, the crystals should be transferred to fresh paper. The disadvantage of this method of rapid drying is that the recrystallised product is liable to become contaminated with the Alter paper flbre. 

It is instructive for the student to construct a rough melting point diagram (compare Section 1,13 and Fig. 1,12, 1) for mixtures of cinnamic acid and urea. Weigh out 1 00 g. each of the two finely powdered components, and divide each into ten approximately equal portions on a sheet of clean, smooth paper. Mix 4 portions of cinnamic acid (A) with 1 portion of urea B) intimately with the aid of a spatula on a glass slide, and determine the melting point (the temperature at which the mixture just becomes completely fluid is noted). Repeat the procedure for 3 parts of A and 2 parts oiB 2 parts of A and 3 parts of B and 1 part of A and 4 parts of B. Tabulate your results as follows —... 

Place 10 ml. of pure benzaldehyde (Section IV,115) and 100 ml. of concentrated aininonia solution (sp. gr. 0-88) in a 250 ml. wide-mouthed reagent bottle. Cork the bottle securely, shake vigorously for 10 minutes and allow to stand with occasional shaking for 24 hours. By this time the benzaldehyde should be converted into a hard mass of hydrobenz-amide. Break up the solid mass with a spatula or a thick glass rod, filter with suction, wash with water, and drain thoroughly. RecrystalUse from absolute alcohol (or absolute methylated spirit). The yield of hydrobenzamide (colourless crystals), m.p. 101°, is 7 g. It is easily hydrolysed by cold dilute acids. 

The residue (5) in the distilhng flask may stUl contain a water-soluble, non-volatile acid. Cool the acid solution, neutralise it with dilute sodium hydroxide solution to Congo red, and evaporate to dryness on a water bath under reduced pressure (water pump). Heat a httle of the residual salt (G) upon the tip of a nickel spatula in a Bunsen flame and observe whether any charring takes place. If charring occurs, thus... 

Step 3. The non-steam-volatile compounds. The alkaline solution (82) remaining in the distiUing flask from Step 2 may contain water-soluble, non-volatile acidic, basic or neutral compounds. Add dilute sulphuric acid until the solution is just acid to Congo red, evaporate to dryness, and extract the residual solid with boiling absolute ethyl alcohol extraction is complete when the undissolved salt exhibits no sign of charring when heated on a metal spatula in the Bunsen flame. Evaporate the alcoholic solution to dryness and identify the residue. 

Chemical Analysis. The presence of siUcones in a sample can be ascertained quaUtatively by burning a small amount of the sample on the tip of a spatula. SiUcones bum with a characteristic sparkly flame and emit a white sooty smoke on combustion. A white ashen residue is often deposited as well. If this residue dissolves and becomes volatile when heated with hydrofluoric acid, it is most likely a siUceous residue (437). Quantitative measurement of total sihcon in a sample is often accompHshed indirectly, by converting the species to siUca or siUcate, followed by deterrnination of the heteropoly blue sihcomolybdate, which absorbs at 800 nm, using atomic spectroscopy or uv spectroscopy (438—443). Pyrolysis gc followed by mass spectroscopic detection of the pyrolysate is a particularly sensitive tool for identifying siUcones (442,443). This technique rehes on the pyrolytic conversion of siUcones to cycHcs, predominantly to [541-05-9] which is readily detected and quantified (eq. 37). 

With any chemical treatment system, the main task is one of getting the chemical thoroughly mixed with the solids without degrading the floes which are formed. For those slurries that are relatively fluid, the chemical can frequently be added and mixed satisfactorily using a relatively wide spatula. However, for those thick, relatively viscous slurries, a power mixer will be required. In this case, the mixer should be stopped about one second after the last of the flocculant is added. Should this approach be required, it means that a suitably designed addition system must be supplied with the full-scale instaUation in order to do an effective job of flocculation. 

Agitation by a wide spatula may be substituted for hand agitation, but only after it has been determined by feel that the spatula will provide the needed agitation. If this cannot be done, then confirmation of proper agitation must be based on back-calculated feed solids concentrations and/or particle size analyses of the filter cakes. 

Agitate the slurry by hand or with a wide spatula to maintain a homogeneous suspension. Immerse the test leaf face downward to approximately one-half the depth of the slurry. 

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