BREAD 505 



or in that of ite phosphate, could not have been found except a salt of alumina 

 to "wit, alum had been used by tho baker. When, therefore, the exact amount 

 of alumina has to be determined, the precipitate in question should be submitted 

 to further treatment in order to separate the alumina ; and this can bo done easily 

 and rapidly by dissolving the precipitate in nitric acid, adding a little metallic tin to 

 the liquor, and boiling. The tin becomes rapidly oxidised, and remains in the state 

 of an insoluble white powder, which is a mixture of peroxide of tin and of phosphate 

 of tin, at the expense of all the phosphoric acid of any earthy phosphate which may 

 have been present. The whole mass is evaporated to dryness, and the dry residue ia 

 then treated by water and filtered, in order to separate the insoluble white powder, 

 and the filtrate which contains the alumina should now be supersaturated with car- 

 bonate of ammonia. If a precipitate is formed, it is pure alumina. The white insoluble 

 pnwder, after washing, may be dissolved in hydrochloric acid, and after diluting the 

 solution with water, the tin may be precipitated therefrom by passing through it a 

 stream of sulphuretted hydrogen to supersaturation*, leaving at rest for ten or twelve 

 hours, filtering, boiling the filtrate until all odour of sulphuretted hydrogen has disap- 

 peared ; an excess of nitrate of silver is then added, and the liquor filtered, to sepa- 

 rate the chloride of silver produced, and exactly neutralising the filtrate with ammonia ; 

 and if a lemon-yellow precipitate is produced, immediately soluble in the slightest 

 excess of either ammonia or nitric acid, it is basic phosphate of silver (3AgO), PhO 5 , 

 the precipitate obtained in the first instance being thus proved to be phosphate of 

 alumina. The pure alumina obtained may now be collected on a filter, washed with 

 boiling water, thoroughly dried, and then ignited and weighed. One grain of alumina 

 represents 9 - 027 grains of crystallised alum. 



In testing bread for alum, it should be borne in mind, however, that the water used 

 for making the dough generally contains a certain quantity of sulphates, and that a pre- 

 cipitate of sulphate of barytes will therefore be very frequently obtained, though much 

 less considerable than when alum has been used. Some waters called ' selenitous ' con- 

 tain so much sulphate of lime in solution, that if they were used in making the dough, 

 chloride of barium would afford, of course, a considerable precipitate. For these 

 reasons, therefore, the separation and identification of alumina are the only reliable 

 proofs ; because, as that earth does not exist normally in any shape in wheat or com- 

 mon salt otherwise than in traces, the proof that alum has been used becomes irre- 

 sistible when we find, on the one hand, alumina, and, on the other, a more considerable 

 amount of sulphate of barytes than, except under the most extraordinary circum- 

 stances, genuine bread would yield. 



Sulphate of copper, like alum, possesses the property of hardening gluten, and thus, 

 with a flour of inferior quality, bread can be made of good appearance, as if a superior 

 flour had been used. 



The use of sulphate of copper in bread is said to have originated about 25 or 30 years 

 ago with the bakers of Belgium. 



M. Kuhlmann, Professor of Chemistry at Lille, having been called upon several 

 times by the courts of justice to examine, by chemical processes, bread suspected of 

 containing substances injurious to health, collected some interesting facts upon tho 

 subject, which were published under the direction of the central council of salubrity 

 of the department du Nord. 



For some time public attention has been drawn to an odious fraud committed by a 

 great many bakers in the north of France and in Belgium, the introduction of a 

 certain quantity of sulphate of copper into their bread. When tho flour was made 

 from bad grain, this adulteration was very generally practised, as was proved by .many 

 convictions and confessions of the guilty persons. When the dough does not rise well 

 in tho fermentation (le pain pousse plat), this inconvenience was found to be obviated 

 by the addition of blue vitriol, which was supposed also to cause the flour to retain 

 more water. The quantity of blue vitriol added is extremely small, and it is never 

 done in presence of strangers, because it is reckoned a valuable secret. It occasions 

 no economy of yeast, but rather the reverse. In a litre (about a quart) of water, an 

 ounce of sulphate of copper is dissolved ; and of this solution a wine-glassful is mixed 

 with the water necessary for 50 quartern or 4-pound loaves. 



Lime water has been recommended by Liebig as a means of improving the bread 

 made from inferior flour, or of flour slightly damaged by keeping, by warehousing, or 

 during transport in ships ; and this method, at tho meeting of the British Association at 

 Glasgow, in 1855, was reported as having been tried to a somewhat considerable 

 extent by the bakers of that town, and with success ; the bread kneaded with lime- 

 water, instead of pure water, being of good appearance, good taste, good texture, and 

 free from tho sour taste which invariably belongs to alumod or even to genuine bread ; 

 admitting all this to be true, still wo should deprecate the use of lime-water in bread, 

 because it cannot be done with impunity ; however small tho dose of additional matter 



