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XL. On the Agency of the Carlonate of Magnesia in improving 

 Bread made from the new Flour. By Edmund Davy, Esq. 

 Professcr of Chemistry, and Secretary to the Cork Institution. 



J To Mr. Till"ch. 



Dear SfR, — jNa recent communication "'', I stated that new 

 seconds flour, ot indifferent or bad Cjuality, is materially improved 

 ior the purpose of makin"' bread, when the common carbonate 

 of magnesia is well mixed with it in the proportion of from 20 

 to iO grains to a pound of flour. 



wSince I announced this fact, I have made a number of com- 

 parative experiments on the worst seconds flour 1 could procure, 

 witii and without the addition of the magnesia; and the residts 

 have uniformly been satisfactory. The ethcacy of this substance 

 has also been repeatedly proved by trialsinade in Cork, and in 

 different parts both of Ireland and England. 



In a few cases, however, it has been saifl, the magnesia failed 

 to produce the desired effect on the new flour; at which 1 am 

 not surprised ; for to my knowledge the calcined magnesia has 

 in some instances been used instead of the common carlonate, 

 and there is too much reason to apprehend this last substance 

 has in other cases been adulterated by admixture with foreign 

 bodies. In an early stage of my experiments, I found the cal- 

 cined magnesia (when used in the quantity of from 20 to 30 

 grains to a pound of flour) to injure the colour of the bread and 

 to render it heavy : and in the proportion of 40 grains to a 

 jjound it even changed the colour of the dough, and made it as- 

 sume a yellow hue, not unlike that tint imparted by saffron. In 

 the proportion of 12 grains to a pound of flour, however, the 

 calcined magnesia improved the bread, but not nearly to the 

 same extent as tlie carbonate. 



There certainly may exist a difference of opinion as to the 

 quantity of im])rovement effected in the bread by the magnesia. 

 Slight circumstances, by no means easy to appreciate, may in 

 different cases materially alter the nature of results. But no one 

 who has fairly tried the magnesia, in the way I have recom- 

 mended, can hesitate to admit the fact. I venture to speak con- 

 fidently from experience. I do it under the full conviction that, 

 whilst too much caution cannot be exercised in drawing con- 

 clusions from one or two hasty trials, the most legitimate in- 

 ferences may be deduced from experiments carefully made and 

 tre(|uently repeated. 



In tlie communication to which I have alluded, I merely 

 fiintcd at the probal)le agency of the magnesia in correcting the 

 bad qualities of the new flour. I now beg leave to notice the cir- 



• See Phil. Mag. for December 1816. 



Vol.49. No.227. iWarc/t 1817. L cumstances 



