appears that those who habitually eat butter and meat preserved with borax might be consuming half a gram or a little more of bóric acid per day. But preserved meats are not regularly eaten, and hence the quantity mentioned is likely to be overestimated. It would be unwise to affirm in a case of this kind, in the light of the data obtained by the experiments, that such a minimum consumption of borax, and especially when not a continuous one, would prove deleterious within any reasonable time of observation. The question then arises, Does the absence of such proof or the impracticability of obtaining it serve as a justifiable excuse for the use of this preservative? This question ought not to be decided alone, because the principle of the decision must stand, not only for boric acid and borax, but for every preservative used in foods. In other words, whatever principle is established for judgment as to the use of boric acid in small portions must also be applied to the use of every other preservative used in foods. The principle must also be still further extended, so that whatever may be established as regards butter or meat must be admitted in respect of every other substance used in food. Hence, before admitting the full force of the argument based on minimal quantities, the full significance of such an admission must be considered and the practically unlimited extent of its application acknowledged. This leads to the discussion of the fact that in the majority of cases the labor of freeing the system from added preservatives falls principally upon the kidneys. In the method of life in vogue in this country the kidneys are already hard-worked organs. Americans probably eat more freely than the citizens of almost any other country, with the possible exception of England. Large quantities of nitrogenous foods are consumed. In the breaking down of the nitrogenous tissues the kidneys are the chief organs for the excretion of the debris. The addition of any further burden, therefore, no matter how minute, is to be deplored. If, however, the principle be admitted that injurious substances may be used in such small quantities as to be practically harmless, then we find the way open for loading upon the kidneys many different functions in addition to those which they now discharge. If they may be justly called upon to eliminate the small quantities of boric acid added in food, they can not logically be freed from the necessity of eliminating also minute quantities of salicylic acid, saccharin, sulphurous acids and sulphites, together with the whole list of the remaining preservatives, which are eliminated principally through the kidneys. It would be useless to contend that the occasional consumption of small quantities of boric acid in a sausage, in butter, or in preserved meat would produce even upon delicate stomachs any continuing deleterious effect which could be detected by any of the means at our disposal, but naturally it seems that this admission does not in any way justify the indiscriminate use of this preservative in food products, implying, as it would, the equal right of all other preservatives of a like character to exist in food products without restriction. It appears, therefore, that there is no convincing force in the argument for the use of small quantities unless it can be established that there is only a single preservative used in foods, that this preservative is used in only a few foods, that it will be consumed in extremely minute quantities, and that the foods in which it is found are consumed at irregular intervals and in small quantities. On the other hand, the logical conclusion which seems to follow from the data at our disposal is that boric acid and equivalent amounts of borax in certain quantities should be restricted to those cases where the necessity therefor is clearly manifest, and where it is demonstrable that other methods of food preservation are not applicable and that without the use of such a preservative the deleterious effects produced by the foods themselves, by reason of decomposition, would be far greater than could possibly come from the use of the preservative in minimum quantities. In these cases it would also follow, apparently, as a matter of public information and especially for the protection of the young, the sick and the debilitated, that each article of food should be plainly labeled and branded in regard to the character and quantity of the preservative employed. Borax and boric acid are regarded by most experts as the least harmful of the antiseptics usually employed. Whether this is a true view of the matter or not remains to be determined by subsequent experiments. It is evident, however, from the results of experimental work that the miscellaneous and premeditated use of these antiseptics in food is reprehensible. There may be occasions when the use of borax is advisable, as, for instance, where butter must be shipped many thousands of miles before it is used or where meats are to be sent across the ocean, and perhaps in various other instances which render imperative the use of a preserving agent. It follows, therefore, that foods should only be preserved with a view to special use. When they are intended for consumption within a short time and for the ordinary continuance of life, it does not seem necessary that any antiseptic should be used, as the food can be perfectly preserved by unobjectionable methods in some of the ways indicated above. Where foods are prepared for various purposes, such as long journeys, excursions, voyages of discovery, etc., as indicated above, it appears that borax could be employed properly if its use is demanded by those who order the food, and if the food products are plainly labeled as having been preserved by this substance. It is, moreover, evident that eating small quantities of borax in food, occasionally, would not prove of any lasting injury to the ordinary citizen in good health, but the weak and feeble must be protected, and it is entirely within the grounds of reason that even a very small quantity of an antiseptic of this kind would prove very harmful to a disordered stomach. The safest rule, therefore, to follow is to exclude these bodies from food except when their use is imperative, and then the quantity of the antiseptic employed should be plainly stated in such a way that the consumer may know what he is eating. Similar experiments to the above have been conducted with salicylic, benzoic and sulphurous acids, but the results of the experimental work have not yet been compiled nor have the conclusions been drawn. This work is to be continued during the coming year, when it is our purpose to determine the effects of formaldehyde and coloring matter, when added to food, upon health and digestion. The Value of the Flame of Combustibles. BY P. MAHLER, Civil Engineer of Mines. Translated from the "Revue Universelle des Mines," Volume V, 4th Series, page 1, 48th year, 1904, By B. F. ISHERWOOD, I. Value of the Flame of Combustibles. The calorific power and the chemical composition are, in general, sufficient elements of comparison between natural combustibles. These data permit, notably, the calculation of the value of flames, and the question may be asked whether this calculation has any practical utility. The value of the flame of a combustible is the same thing as its temperature of combustion under constant pressure. It is measured by the thermometric degrees through which the gaseous products of the combustion are raised, supposing them to be heated by all the heat due to the combustion and solely by that heat. It must also be admitted that the combustion is complete and that it is realized by the aid of air under the atmospheric pressure, always nearly constant, as it takes place on grates. The preceding definition is in accord as much as possible with industrial conditions; but, in fact, the temperature of combustion is a theoretical number defining with precision a limit that practical industry cannot exceed with any given combustible and for the given bodies to be heated; and it seems interesting to compare different coals from this point of view. The calorimetrical bomb and the elementary analysis having supplied* me with the necesary data for the calculation of temperatures of combustion, I have determined the value of the flames of a complete series of combustibles. * "Etude sur les Combustibles," by P. Mahler, 1903, published by Beranger. II. Determination of the Temperature of Combustion. The determination of the temperature of combustion is done without difficulty, and the method I have followed is an old one. Nevertheless, I will cite the principal points because they can be of service to engineers in many cases, as in the examination of the functioning of furnaces,* and of the economic results of gas-motors calculated from the temperature of detonation of an explosive, etc. Be q the calorific power of unit of weight of a combustible under constant pressure. Be Cm the mean specific heatt between 0 and T, absolute temperature of any one of the gases whatever composing the gases of combustion; let it be taken in relation to the weight of the gas which occupies a volume equal to 22.3 liters. Be N the number of molecules (22.3 liters) of this gas resulting from the combustion. As the energy of a gaseous mass depends wholly on its temperature, and as the coal in question is burned at a temperature very near o° C. or To, the heating due to the combustion between T, and T, is, according to our hypothesis, united closely to the calorific power by the expression Σ signifying that the gases of combustion are a mixture of several gases for which N and Cm have special values. The analysis of the combustible gives N, and if Cm were constant, we could easily deduce from the above equation T1, since the temperature sought for = T1 — 273° in Cen℗ tigrade degrees. Ti But the problem is more complex. Messieurs Mallard and Le Chatelier have demonstrated that the specific heat of the gases of combustion increase with their temperature, this phenomenon becoming very sensible at high tempera * "Le Chauffage Industriel," by Mr. E. Damour. † dq being the elementary heating of 1 kilogramme, the true specific heat at the temperature t is by definition. dq dt = C Between the true heat and the mean heat from o to t, we have, in general, the relation : |