November, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
than nitroglycerin or the common mixture of nitroglycerin and nitropolyglycerin. Animal Poisoning
Experience in the laboratory handling of the compound has shown that the effect of glycol dinitrate upon the human system when absorbed through the skin or inhaled in vapor form is almost identical with that of nitroglycerin. It produces dilation of the blood vessels, acceleration of the heart
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action, and a severe headache. It is considered that these effects are not so prolonged in the case of glycol dinitrate as those of nitroglycerin. As already shown, the vapor pressure of glycol dinitrate is much higher than that of nitroglycerin; therefore inhalation of sufficient vapor to produce unpleasant effects is much more likely to occur in the course of handling. However, it has been found that persons constantly working in proximity to the material soon develop an immunity to its usual effects just as is the case with nitroglycerin.
The S‘mall-Scale to Factory Proportion’ By Washington Platt MBRRELL-SOULB Co., SYRACUSE, N. Y.
VEN in well-established factory processes constant capital letters. Using this system, let us abbreviate our experiments must be conducted. These may arise proportion as follows: from necessity, through the use of different shipments Let n = new method small-scale results of raw material, or as a deliberate attempt to improve factory o = old method small-scale results results. In either case, the difficulties and expense involved N = NEW METHOD FACTORY RESULTS in experimenting with new formulas and methods in large0 = OLD METHOD FACTORY RESULTS scale production are well known. It is therefore desirable Using these easily remembered abbreviations, our proto conduct preliminary experiments on a small scale where portion becomes n:o = N : O . ever possible. To see what this means, let us take the experimental Such small-scale experiments are usually, for reasons of economy, much too small to be classed as “semiworks” baking test of bread as an example. Suppose we are baking runs. They are carried out with small, simple equipment. our commercial bread with a certain brand of flour. We Two of the best-known examples in the food industries are propose to try a new brand. We make an experimental the baking test of flour millers and bakers, usually carried baking of both the new and the old flours on a small scale. out with single loaves in an electric oven, anti the experi- If the n loaf is large‘r than the o loaf, then according to this mental mill of the flour miller. Nearly every manufacturer, proportion we can expect N to be larger than 0. If n dough however, has a small steam-jacketed kettle and other appa- requires a longer time to ferment than the o dough, then we ratus with which he can parallel factory processes in miniature can expect the N dough will require a longer time to ferment for experimental purposes. than the 0 dough. In other words, n:o = N:O. Small-scale equipment may be inexpensive and yet exIn this common commercial problem the result required tremely useful as a guide to the factory when formulas (the “unknown” in mathematical language) is N , representing or methods are to be changed. Only too frequently, however, the results of the proposed new method on a factory scale. the valuable information which might be obtained from I n the case of bread, N is the characteristics of the new loaf such equipment is little utilized by those in charge of pro- on a factory scale. N can be quite accurately estimated duction. This occurs through a failure to appreciate what when the other three members of the proportion are d e can properly be expected from small-scale runs and to under- termined. But these three are all easy to obtain. 0 is already known; n and o are easy to obtain because they stand how to interpret and apply their results. Everyone knows that small-scale runs rarely exactly involve small-scale runs only. By means of this proportion, duplicate factory results. For example, a loaf of bread therefore, we may secure a fairly accurate estimate of the made from a small-scale baking test will not be identical with large-scale results to be expected from some proposed new bread made from the same formula in the commercial bakery. method before trying the new method in the factory. The time of fermentation, size, and appearance of the loaf In arithmetic, we know’that three terms of a proportion will all be different. Again, in vegetable-oil refining the must be known before the fourth can be determined. This yield from refining a one-pound experimental batch of crude is equally true of the proportion here considered. Realioil is not exactly l/lo,ooo of the yield obtained in the factory zation of the necessity of knowing three terms helps us to from a 10,000-pound batch. These discrepancies have avoid some of the errors frequently made in attempting led some “practical” men to the extreme statement that to estimate factory results ( N ) directly from small-scale “you can tell nothing about what factory results will be from runs (n). observing small-scale runs.” Many other people, seeing Common Errors in Applying New Methods that small-scale results are necessarily different from factory results, have failed to grasp the true relation between the The most common error when a new method is proposed two. This relation is most clearly and briefly expressed by what may be called the “Small Scale to Factory Proportion.” is to make up a small-scale run by the new method (n) and compare this directly with the factory product made by New small-scale results : old small-scale results = the old method (0). In other words, we compare n directly NEW FACTORY RESULTS : OLD FACTORY RGSULTS with 0. Such a comparison cannot be trustworthy as we For ease of memory, small-scale results have been ex- have two important factors varying a t the same time. There pressed by small letters, and large-scale factory results by is the variation between a factory-made and a small-scale product, and a t the same time, the variation between the 1 Received April 9, 1926.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
new process and the old process. The proportion tells us, however, that we must compare the small-scale run by the new process (n) with the small-scale run by the old process (o), to see how much difference is made by the change in process. Then we compare the small-scale run by the old process (o), with the factory run by the old process (0), to see how much difference is made by the change from smallscale to factory-scale. Here, we have only one factor varying in each comparison; hence, we can draw more reliable conclusions. A second common error is to attempt to design an entirely new commercial process with only small-scale runs as a basis, without any large-scale tests or “semiworks” runs. The dangers of doing this have often been described.2 An attempt to set up the “Small Scale to Factory Proportion” brings us to the same conclusion. In developing an entirely new commercial process we have the smallscale runs but no factory-scale results whatever. We have two terms of the proportion, but not three, and we know that three terms are necessary for the solution of a proportion. Many people think that the small-scale products ought to be the same as the factory products and, as this is seldom the case, that little can be learned by small-scale runs. The proportion n:o = N : O clearly shows us, however, that n need not equal N and that o need not equal 0. In fact, they seldom do so. 14, 2
Whiting, 8th Intern. Cong. A g p l . Chem., Section Xa, p. 204.
Vol. 18, No. 11
Limitations
Now for the limitations of this proportion. First, it must be emphasized that it gives only relative terms and that results must be expressed as “more” or “less.” Results are not strictly quantitative and the proportion is not a rigid mathematical equation, though it has been written as such for the sake of brevity and simplicity. One side is only approximately equal to the other, so that, strictly speaking, our proportion should be written n:o = approximately N :0. Another precaution to be borne in mind is that the smallscale method must involve all the essential factors of the factory method. The more nearly the small-scale formula, times, temperatures, and methods of handling approximate the large-scale factory conditions, the more reliable will this proportion be. Experience in comparing small-scale results with factory results in any given series of experiments will indicate how closely this “Small Scale to Factory Proportion” can be followed. Wherever small-scale runs are made it is necessary to get an idea of this, just as it is necessary to form an idea of the size of the experimental error in any experimentation. If small-scale conditions differ so much from factory conditions that results on a small scale vary without relation to results on a large scale, this fact should be known as soon as possible. 8uch small-scale runs are evidently actually misleading and not worth making a t all, being like work in which the experimental error is greater than the differences to be observed.
The Chemistry of Gasolines’ Particularly with Respect to Gum Formation and Discoloration By Benjamin T. Brooks 40
EAST4 1 s ~S T , N s w YORK,N. Y.
The first step in the formation of gum in cracked gasolines is the formation of organic peroxides. These break up in a complex manner, with the formation of aldehydes, ketones, including formaldehyde, water, carbon dioxide, and further oxidation to organic acids. The fluid gum observed in gasoline consists mostly of organic peroxides and fluid aldehydes and ketones; old fully oxidized resin, after expelling volatile products, is resin acids, not aldehyde condensation products. Small proportions of easily oxidizable hydrocarbons, such as diolefins, promote the formation of large proportions of gum. Oxidation of ordinary olefins with “gum” formation also occurs, but at a very much slower rate. . . .. .. .
The most common cause of the discoloration of gasolines and kerosenes is the development of a trace of acidity. Sulfur dioxide and its oxidation to sulfuric acid is the most common cause of this acidity. The known oxidation of mercaptans and alkyl disulfides to sulfonic acids may also cause discoloration. Gasolines which have not been acid-treated may develop acidity and discoloration. The function of steam in redistilling acid-treated cracked gasolines is to take up the sulfur dioxide formed during distillation. Alkalies or oil-soluble bases prevent discoloration by developed acidity.
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of the practical value of the motor fuel, pronounced color of a gasoline, when not artificially colored, may be, and generally is, an indication of poor refining, and the complaint that color has no significance usually comes from refiners who have difficulty in producing gasolines up to the usual commercial standards. Like the question of color, gum formation in gasoline claimed public notice when cracked gasoline began to be widely marketed. The first to mention a gum test or specification was apparently E. W. Dean,2 who states that it was devised by F. C. Robinson and his associates in the Atlantic Refining Company, as a test to be applied to aviation gasoline. Dean suggests that amounts of gum up to 0.03 per cent
N T H E present paper no attempt is made to correlate
the color or gum-forming properties of gasolines with their value as motor fuel. Generally, these and other tests have been self-imposed by refiners themselves, probably to insure that their products are above any possible criticism. Practically all refiners manufacture gasoline far better with respect to color than was required by U. S. Government specifications, but since color is one of the few qualities which the ordinary consumer can easily note, this is still s, standard which most distributors prefer to maintain. While it is generally admitted that color, of itself, is not a good criterion 1 Presented under the title “The Chemistry of Gasoline, with Respect to Color, Stability, and Gum Formation” before the Division of Petroleum Chemistry a t the 71st Meeting of the American Chemical Society, Tulsa, Okla., April 6 to 9, 1926.
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Bur. Mines, Tech. P a g e 914.
