A laboratory manual of foods and cookery

When all is ready, put i tbsp. of an acid or hot water respectively into a test tube until all have been used. Several phenomena will be observed. Note the evolution of gas, rapidity with which given off, comparative amount of carbonate of lime deposited. Conclude the corresponding amount of carbon dioxide given off. Tabulate and compare the results. 176. - - If the facilities of the chemical laboratory are available, make the experiment with cream of tartar quantitatively, using pure substances. 177. - - In the experiment with cream of tartar, it will be necessary to add water before the action will take place. What does this explain in regard to baking powder? Why is corn starch or flour used in the manufacture of baking powder ? 178. - • Test | tsp. of baking powder with i tbsp. hot water. Assuming that the baking powder is a mixture of sodium bicarbonate and an acid salt, can you determine the nature of the latter by chemical analysis ? 179. Prepare baking powder according to the following proportion : | Ib. cream tartar \ Ib. baking soda \ Ib. corn starch Sift six times Yeasts 180. - - Fermentation of molasses. Into a common test tube or any glass vial, place a solution made by mixing one spoonful of molasses with ten spoonfuls of water. Rub up a little compressed yeast in water and put a few drops into the tube of molasses water. Set aside in a warm place and let it stand for about 24 hours. At the end of this time a vigorous fermentation will be seen. The liquid will have become somewhat cloudy, numerous bubbles can be seen rising through it, a froth forms on top, and a mass of sediment soon collects at the bottom. The bubbles are the carbon dioxide which is escaping into the air ; the sediment at the bottom is the growing mass of yeast, and the alcohol, which looks like water, is dissolved in the liquid and is, of course, invisible. 181. - - Proof of the nature of the gas. Prepare two tubes. In tube A place molasses and water inoculated with several drops of yeast, as in the last experiment. Put the cork in place and insert the other end of the tube into a second tube underneath the surface of some clear limewater. Set aside in a warm place until vigorous fermentation occurs. Note the bubbles of gas that arise from the fermenting tube and bubble up through the limewater. The limewater soon becomes turbid, showing that the gas contains carbon dioxide. 182. — Rub a bit of yeast cake in a little water so as to make a slightly cloudy solution. Place a drop of the solution upon a microscope slide, cover with a cover glass, and examine first with a f-inch objective. Note that the water seems to be filled with very minute dots. Study with a higher power (^ in. objective). Examine the yeast cells, noting the shape and comparative size.