May 



^] 



SCIENCE. 



423 



tion of the State that one enterprising manufacturer offered a 

 wagon with each purchase of a certain number of cans. 



In commenting on this report of Professor Cornwall, the dairy 

 commissioner, Dr. Newton, says that from inquiries made in vari- 

 ous parts of New Jersey, and from knowledge gained in conversa- 

 tion with those conversant with the habits of all classes of people, 

 he should say that the use of baking-powders is confined to the 

 preparation of biscuits, cake, and articles other than bread. The 

 biscuit thus prepared is usually eaten hot, and constitutes a very 

 large portion of the dietary of the working-people. In the homes 

 of many of the wage-workers, this biscuit made with baking- 

 powder is the usual form of bread used for at least two-thirds of 

 the time ; fresh, yeast-leavened bread being the exception. This, 

 of course, does not obtain in the large cities, where bread is easily 

 bought. It may be said, without fear of contradiction, that bread 

 made by means of yeast is by far the most satisfactory and the 

 most healthful of all the preparations of flour. It contains no resi- 

 due about which there can be any controversy, it contains no added 

 chemical; it retains, with but little change, the nutritive elements 

 of the flour. Hence, while baking-powders may answer for occa- 

 sional use, they cannot be recommended as a complete substitute 

 for yeast, as their action is different from and the product dissimilar 

 to that obtained from fermentation. 



A baking-powder should answer to all of the following require- 

 ments : I. It should generate the maximum amount of gas ; 2. It 

 should contain no unhealthful ingredients ; 3. It should leave in 

 the loaf no unhealthful residue ; 4. The elements should be com- 

 bined in such proportions that the residue is neutral in re-action. 



Dr. Newton further says that the evidence is conclusive, and 

 certainly points to these facts : that alum residue does affect diges- 

 tion, and that these residues are more or less soluble, and are 

 carried into the system. Hence it is suggested, that, if any person 

 wishes to avoid a possible danger to health, he should refuse to 

 buy alum-powders. It must be stated, however, that the evidence 

 in the case is not as strong as with other chemical agents, and we 

 cannot speak of the results following the constant ingestion of 

 small quantities of the soluble alum compounds with the certainty 

 that we do when considering lead and other toxic agents, which 

 are poisonous when taken in very minute quantities and continu- 

 ously. All that he can do officially, while there is yet doubt on 

 this question, is to give the public the benefit of that doubt, and 

 advise the use of these preparations with great caution until the 

 problem is positively settled by experiments on the lower animals. 

 As will be seen by reading Professor Cornwall's paper, seme alum 

 combinations are known to be dangerous to health : these he has 

 indicated. He cautions the public that baking-powders sold by 

 weight, and without any name on the package, are to be avoided, 

 as any manufacturer responsible for his preparations will not be 

 ashamed to print his name on the label. 



In the introduction to his report. Professor Cornwall remarks, 

 that although nothing is so well adapted as yeast for making a 

 palatable and digestible bread, yet their greater convenience or the 

 necessities of the case may sometimes be a reason for using bak- 

 ing-powders even for making bread, and they are very largely used 

 in preparing various articles of food which largely take the place of 

 bread. It becomes, therefore, a very important question to deter- 

 mine the probable effects of the many different kinds of baking- 

 powders on the health of the consumer. 



He explains the action of baking-powders as follows : The bak- 

 ing-powders render the bread"- light, through the action of gas set 

 free in the dough. This gas is almost exclusively carbonic-acid gas, 

 the carbon dioxide of the chemist. The carbonic acid is set free 

 from bicarbonate of soda by the action of some acid substance, 

 which yields a part or the whole of its acid to the soda, thereby 

 expelling the carbonic acid. 



Carbonate of ammonia has been to some extent employed. This 

 substance is solid at ordinary lemperatures, and is converted into 

 gas by the heat in baking, but is not alone suitable for a baking- 

 powder, because it may easily remain to some extent in the bread 

 after baking, imparting to it not only an unpleasant taste, but pos- 

 sibly, even probably, unwholesome properties. 



1 For 

 baking-powdi 



rLicles made with 



Formerly the cook made the baking-powder, when needed, by 

 mixing in due proportions the two salts commonly used, — cream- 

 of-tartar and bicarbonate of soda. The cream-of-tartar (bitartrate 

 of potash) contains more of the tartaric acid than is necessary to 

 neutralize the potash in it, and this excess of acid liberates the 

 carbonic acid from the bicarbonate of soda. The re-action takes 

 place only when the two salts become dissolved in the dough, and 

 these salts were especially adapted to the purpose because they 

 dissolve but slowly ; so that there is a continual and gradual lib- 

 eration of the gas, keeping the bread light until the baking is fin- 

 ished. Bicarbonate of soda is better than simple carbonate, also, 

 because it yields twice as much gas. 



There were serious objections to the old-fashioned process. 

 Apart from impurities in the salts, which are quite as prevalent in 

 some of the modern baking-powders, the cook needed to exercise 

 unusual care in measuring the two salts, so as to avoid getting too 

 much of one or the other ; and quite as great care was needed to 

 thoroughly mix the two, so that they might exercise their full ac- 

 tion on one another, without which the familiar yellowish or brown- 

 ish " soda " spots would be produced. A really well-made baking- 

 powder obviates all the evils resulting from these causes, as well 

 as from the use of impure or deteriorated materials. 



The requisites of a good baking-powder are (i) that the ingre- 

 dients, in the quantities used, shall not injure the health of the 

 consumer; (2) that the powder shall yield the largest amount of 

 gas that can be obtained from wholesome ingredients, and in such 

 a way as to produce the best effects (boiled with water, it should 

 give a neutral or very nearly neutral solution); (3) that the powder 

 shall keep its strength, and also not cake or become lumpy under 

 the ordinary conditions of storage and use. 



The caking of the powder is due to the fact that some of the 

 active ingredients are often of such a nature as readily to absorb 

 moisture from the air, so that they partly dissolve, and not only 

 cause caking, but also loss of " strength " through the escape of 

 carbonic-acid gas. This evil is greatly reduced by the use of well- 

 dried materials, and by the addition of dry starch-powder, wheat- 

 flour, or similar farinaceous substance, so that a well-made powder 

 loses very little strength. In good cream-of-tartar baking-powders, 

 about twenty per cent of such a " filling " body is often used. 

 More than this is unnecessary, and simply lowers the cost of the 

 product. A little less is sometimes used. In the majority of alum- 

 powders the strength is only one-third or one-half what it might 

 be ; and in many cases this is, no doubt, due to excess of the starch 

 or flour thus sold at the price of baking-powder. It may be argued 

 that the strength of the powders is purposely kept down to a stand- 

 ard that will permit the use of the customary " two teaspoonfuls. 



The statements on labels, that a powder " is made from pure 

 ingredients," has little significance, unless the ingredients of the 

 po'wders are also given. An alum-powder may be made of pure 

 alum ; a mixed powder may contain pure bisulphate of soda and 

 pure tartaric acid ; even an acid-phosphate-of-lime powder may be 

 made of pure materials, so far as concerns the addition of any 

 adulterant by the compounder, and yet the acid phosphate may be 

 full of sulphate of lime, originally present in it by the nature of the 

 process of manufacture. Thus, a maker of baking-powder might 

 be sending out an article containing much terra alba (sulphate of 

 lime) ; and yet, because he knew he had not put in any terra alba 

 as such, he would claim that his powder was pure. 

 Cream-of-Tartar Powders. 



The cream-of-tartar itself is a natural constituent of grape- juice, 

 and probably no material has ever been devised for making baking- 

 powders that is open to less objection than cream-of-tartar, unless 

 possibly the acid phosphates. 



Acid-Phosphate-of-Lime Powders. 



The acid phosphate of lime (also called superphosphate of Hme> 

 has of late been much used in baking-powders, and there seems to 

 be no physiological objection to its use. Indeed, it is claimed that 

 its use restores to the finest wheat-flour the phosphoric acid which 

 is so necessary to our health, and which has been in great part re- 

 moved with the bran. Other acid phosphates have been to some 

 extent employed, but the acid phosphate of hme far the most 



