Get at a druggist's a pound of super-car. bonate of soda, and three-quarters of a pound of tartaric acid. Both these articles must be of the very best quality. Prepare an equal number of square blue papers, and square white papers; nicely folded. To be very accurate, weigh the articles alternately. In every blue paper put a hundred grains of the super-carbonate of soda, and in each white paper ninety grains of tartaric acid; and then fold them up so as to secure their contents. If you have not suitable scales and weights, you may guess tolerably well at the proportions of the articles by measuring a full tea-spoonful of the soda for each blue paper, and three-quarters of a tea-spoonful of the acid for each white paper. Put them up in boxes, and keep them in a dry place. The contents of one blue paper and of one white paper are considered as one yeast-powder; half the contents of each paper are called half a yeast-powder.

Yeast-powders of themselves have not sufficient power to raise bread or cakes so as to make them light enough to be wholesome. They should only be employed when real yeast, or eggs, are also used. Then they add greatly to the lightness of the cake. They are also an improvement to batter puddings. They must always be added at the last.

To use them, dissolve first the soda in a wine-glass and a half of milk or lukewarm water, and when thoroughly melted, stir it into the batter. Then melt in another cup the acid, with a similar quantity of milk or water, and stir it in at the last.

These powders entirely destroy the flavour of lemon or orange-juice. But they will convert sour milk into sweet. A yeast-powder added to buckwheat batter that has already been raised by real yeast, will render it surprisingly light. One blue and one white powder will suffice for two quarts of batter.