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Home > full pipettes. Their usual form...
Previous Next The best candle and soap tips online! full pipettes. Their usual form is shown in Figs. 9 and 10. The sizes most suitable are 1 litre, 1000 cubic centimetres 176 TECHNICAL TREATISE ON SOAP AND CANDLES. (33.8 fluidojnces), 100 cubic centimetres (3.38 iuidounces). They have, on the neck, a mark, up to which they are filled with the teet-liquids; upon their side they carry the figures of their capacity. Of the smaller sizes a large number are kept at disposal. CYLINDERS FOR MIXING. These two utensils are principally used for producing the titriraetrica' liquids {acids or alkalies). The nnxing cylinder has a stopper of glass, and is graduated from 10 (0.33 fl. oz.) to 1000 cubic centimetres (33.8 8. oza,), see Fia;. 11. These cylinders are represented in Fig. 12, and also graduated from Pis. 12. 100 (3.38 fl. ozs.) to 1000 cubic centimetres — 1 litre (33.8 fl. ozs.). Their stoppers are also made of glass. Tlie most suitable size for mixing cylinders and mixing bottles is 1000 ALKALIMETRY. cubic centimetres = 1 litre (2.1 pints), but others of less capacity are also used. SCALES AND WEIGHTS. The most indispensable of all instruments is a good, sufficiently sensitive, balance or scale, with the accurate weights belonging thereto. For a soap manufactory such a, scale ia good enough which, whan burdened with a weight of 4 ozs., will yet indicate with accuracy when one-half grain additional weight is placed upon it. The absolute correctness of the weights is likewise required. TINCTURE OP LITMUS, COCHINEAL TINCTURE. To ascertain the poirt where, by the additiou of the titrated acid to the alkali, which is to be estimated, or from a titrated alkali to an acid, neutrality will ensue, litmus tincture is usually applied, but in some instances cochineal tincture will serve the 3ame end. Both show by the variation of color wliich they undergo the small overplus of alkali or acid and the point of neutrality. The blue color of the litmus turns by dint of the overp'ns of acid into red, and the color of the acid reddened by the litmus changes into blue by an excess of alkali. The tincture of cochineal is originally of a chestnut-brown color, which, with alkali, Incomes a splendid carmine red, a:id, by adding acid, receives a light brick-red color. Each of these two indicators—the term given to these tinctures—has its advantages and its faults. The tincture of litmus doe3 nit show the beginning of neutrality, since by the teat with carbonated alkalies the cartonie acid becomes free and acts upon the color of the litmus,and produces a coloring which is neither red nor blue; hence the liquid has previously to be warmed in order thereby to remove the carbonic acid, But tliis is troublesome and confusing. This fault, however, the tincture of cochineal does not have; its color is in no wise affected by the free carbonic acid, no warming is needed, and the operation may be performed in one draught. Forinvestigatingthecarbonatedalka-13 178 TECHNICAL TREATISE ON SOAP AND CANDIES- /LKALIMETRY. 173 lies it is in L high degree preferable. But it is most suitable for testing caustic alkalies, especially in concentrated solution, and some experience is required to hit the proper point. Its color suffers in contact with alkalies, a chemical change takes place in consequence thereof; by the neutralization of an acid, not a brick-red color, but a ''.armtrie-red hue appears, which, by inexperienced persons, may easily be confounded with that caused by alkali. If it is intended to make use of the cochineal tincture for testing the caustic alkalies, it would be well to allow the lye to flow upon the normal acid. The tincture of cochineal, when the liquid to be tested contains even a mere trace of oxide of iron, is quite unserviceable. When, however, it ia applicable, it is, without doubt, certainly much more sensitive than the tincture of litmus. TEE PREPARATION OF TINCTURE OF LITMUS. Place 33£grms. (1.175 ozs.) of good commercial litmus in a test-tube, pour about 133£ grins. (4.70 ozs.) of distilled water on it, place it upon a heated stove, frequently shaking it gently. After a lapse of from six to eight hours the intensely blue liquid is drained off from the residuum, to which add again 66§ to 83£ grms. (2.35 to 2.94 ozs.) of water, and let it again stand in the warmth for a short time, and decant when both extracts are mixed. The liquid contains free carbonate of alkali, which is a hindrance to its sensitiveness, and must be removed This is done best and most eompletely by boiling the tincture with about 3 per cent, of the litmus used with finely powdered gypsum, and digesting it for a longer period. By this operation carhonate of lime is produced, as well as sulphate of alkali, which remains dissolved. This tincture assumes, thus prepared, after a few days, a decided lilac shade of color, but it is nevertheless as well for alkalies as for acids in the highest degree sensitive, the smallest overplus of the former making it a pure blue, the smallest overplus of acid decidedly red. At tinea the tincture of litmus shows the peculiarity of losing ks color in a closed flask and turning brown j but it is not for this reason Previous Next
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