October. 1927
I.VDUSTRISL AND ENGI,VEERING CHEMISTRY
1157
Composition of Commercial Chemical Limes’.” By J. S. Rogers BUREAUO F
STAXD.4RDS, \ v A S H I N G T O N ,
H E data herein reported were developed for the purpose of preparing specifications for chemical lime. The preparation of these data was undertaken a t the request of the Interdepartmental Conference on Chemical Lime, which is composed of representatives of the various governmental establishments interested in lime and its application. The conference, through the Bureau of Standards, and in cooperation n-it’h the industries interested, prepares and issues recommended specifications for lime suitable for use in the yarious chemical industries. Recently it became necessary, in the preparat.ion of specifications, to determine the composition of representative chemical limes and this study included those constituents present in small amounts. Generally each industrial process using lime requires a product of definite composition for optimum reactions. For example, iron3 has a detrimental effect in bleaching powder in that it accelerates decomposition; manganese4 has :t similar effect; insoluble matter retards slaking of quicklime, abrades processing machinery, etc.; arsenic compounds are obviously objectionable in lime used in products destined for human consumption; and phosphorus is undesirable in lime in the steel industry. Each industry has therefore found it advantageous to set limits on the constituent’sof the lime used. For use in the investigation, thirty-five samples of limesixteen hydrated limes and nineteen quicklimes-.representstive of those used in chemical industries were furnished by producers for analysis.
T
Methods Used The A. S. T. M.6 methods were used as a guide in the analyses of the lime samples, but where desirable and where circumstances warranted, other methods and modifications of the A. S. T. 31. procedure were employed as follows: The silica was dehydrated only once, as data obtained on several samples showed that the second dehydration was unnecessary because of the low silica content of all the samples. Iron was determined in two ways-first, by the dichromate method with noted modifications, and second, colorimetrically. The first method required the reduction of the hot hydrochloric acid solution of the sample with stannous chloride, followed by the addition of mercuric chloride to the cooled solution, and finally titrating with dichromate, using diphenylamine as an inside indicator.6 In the second method the “R203” was precipitated by Blum’s method,’ dissolved in dilute hydrochloric acid and fumed with concentrated sulfuric acid to convert the iron, aluminum hydrates, etc., t o sulfates. The sample was then diluted to a known volume and a n aliquot portion transferred to a Nessler tube. A standard sample of ferrous sulfate was likewise prepared in a Nessler tube and potassium permanganate added dropwise t o each tube until the pink color of both tubes was of the same intensity. Ammonium 1 Presented b y J. ht. Porter and J. S. Rogers under the title “The Composition of Commercial Limes and Their Specification for Industries,” a s a part of the Lime Symposium before the Division of Industrial and Engineering Chemistry a t t h e i 3 r d Meeting of t h e Americ.an Chemical Society, Richmond, Va., April 11 t o 16, 1927. Received August 15, 1927. 2 Published b y permission of the Director of the National Bureau of Standards. a Lunge, “Soda Industry,” Vol. 111, 2nd ed., p. 366. 4 Gill, THISJOURNAL, 16, 577 (1924). 5 Proc. A m . Soc. Tesling M a l e ~ i d25, ~ , 618 (1926): (C26-25T). 8 Knop, J. A m . Ckem. Soc., 4 6 , 263 (1924). 7 Bur. Standards, Sci. Paper 286.
D.
c.
thiocyanate was then added, the solutions diluted to equal volumes and the color intensity compared in a Duboscq colorimeter.* A l u m i n a was determined by subtracting the sum of the oxides of iron, phosphorus, and manganese from the R203 value, and therefore includes any titanium oxide that might be present. Both volumetric and gravimetric methods mere used in determining phosphorus. The first method consisted briefly in dissolving in standard alkali, the ammonium phosphomolybdate, precipitated from a nitric acid solution of the sample, and titrating the excess alkali with standard acid-viz., nitric acid. The second procedure called for the precipitation of phosphorus as h f g S H 4 P O ~6HnO . with subsequent ignition to ?\Ig,P20,, from which weight the phosphorus content was determined.8 The bismuthate method was used for murtgenese, following the conventional method used in steel analysis to determine this element.10 S o arsenic was detected in any of the samples by the Gutzeit method. Calcizim was precipitated once as oxalate and titrated with potassium permanganate solution.5 .l.;ug.izesia was determined in accordance with the procedure given by the Bureau of Standards” using microcosmic salt as the precipitant and igniting the resulting MgNH4P04.6H20 to the pyrophosphate. The sulfur (sos)was precipitated as barium sulfate by adding barium chloride to a 2 per cent hydrochloric acid solution of the sample.3 The carbon dioxide evolved by dissolving the sample in hydrochloric acid was absorbed in ascarite.I2 The loss on ignition equaled the net change obtained by blasting a weighed portion of the sample to constant weight. The solubility iiz 1 : 9 hydrochloric acid was determined by digesting the sample on the steam bath with acid of that concentration for half an hour.
It was noticeable that several of the quicklime samples exhibited a strong tendency to hydrate and carbonate during the exposure to the atmosphere in the necessary handling of the sample. The irregular absorption prevented duplication of results, especially when a considerable period elapsed between analyses. By placing the ground quicklime in a closed desiccator over water, the quicklime hydrated, reaching a state of chemical stability where its coinposition remained constant during the time necessary for analysis. (By this method a small amount of carbon dioxide was left in the desiccator, but this amount was negligible.) This procedure was not necessary in the cases of slow hydrating quicklimes. For the convenience of the reader, the CaO figure on the quicklimes, which were hydrated before analysis, can be calculated to what it would have been in the original lime, assuming a 1 per cent loss on ignition. A 1 per cent loss may be assumed without serious error, as this is approximately the average ignition loss. The following formula indicates a method of calculating the CaO from the hydrated sample: CaO in hydrated sample + (per cent loss + 1)
= 100
Discussion of Results The results are shown in the accompanying table. The silica content of twenty-two samples, representing more than two-thirds of the total number of samples analyzed, Bur. Standards, Circ. 163. hlethods of Chemical Analysis,” Vol. I, p. 362. l o Treadwell and Hall, “Analytical Chemistry,” Vol. 11, p. 617. Bur. Standards, C i r c . 3, 4th ed., p. 7. 1 2 Hillebrand, C . S. Geol. Suvoey, Bull. 7 0 0 . 8
* Scott. “Standard
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1158
Vol. 19, No. 10
C o m p o s i t i o n of C h e m i c a l L i m e s (Figurer in per cent)
INSOLUBLE
SAMPLE Si02
FeiOa 0.04 0.10 0.04 0.10 0.33 0.01 0.14 0.18 0.16 0.19 0.07 0.92 0.31 0.25 0.10 0.04 0.12 0.06 0.07 0.17 0.09 0.01 0.02 0.28 0.04 0.06 0.11 0.06 0.07 0.10 0.02
AlzOa Pa06 MnsO4 14 0.70 ND 0.74 N D (0.0017) 2 0.27 0.26 0.02 N D (0.0025) 0.50 54 ND T 0.74 0.20 2.30 6 T 0.03 2.84 74 0.99 ND T 0.44 84 0.77 0.15 0.01 0.17 9 1.04 0.02 T (0.006) 114 1.50 0.58 T N D (0.0044) 12 1.54 1.75 0.01 T 1.79 13 T 1.17 0.02 0.04 14 ND 0.81 0.01 0.48 ND 15‘ T T 1.03 0.84 16 ND 0.10 3.46 17” 0.76 0.03 4.01 184 T O5 1.73 0.36 19a ND T 0.67 2.32 204 T (0.0059) ND 0.84 0.26 214 0.62 T 0.08 22 1.06 T 0.50 0.01 23 1.08 0.64 N D (0.0024) 0.07 244 0.44 T T 0.85 25O 0.40 1.01 ND N D (0.0044) 0.11 26 0.06 0.03 ND 27 0.66 1.48 T 0.01 284 0.38 T 0.20 0.01 29“ 1.00 T T 0.32 30 1.02 1.12 0.01 N D (0.0015) 31 0.88 1.13 T T 324 0.72 0.17 T N D (0.0044) 0.84 33 T T 1.03 0.65 34 0.58 0.01 ND 0.30 354 T N- D ND 0.38 0.95 36 0.08 ND 0.03 0.68 0.22 375 T 0.08 ND 0.62 0.40 38” 0.82 ND 0.04 ND N D = less than 0.005 per cent; T trace (less than 0.01 per cent). e Quicklimes.
.
%
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is below 1 per cent. Seven samples contain between 1 and 2 per cent, and two samples more than 3 per cent. From the results obtained it does not seem that a maximum limit for Si02 of 1 per cent in limes for chemical purposes would be unreasonable. With the exception of one sample, the iron content was uniformly low; all samples containing less than 1 per cent. The raw samples containing a relatively large amount of iron, but low in manganese, were not badly discoloreda light cream tint. The results show that lime with an iron content of less than 0.5 per cent may be easily secured. The alumina, as determined by difference, exhibited wide variation-from “not detected” to 2.75 per cent. According t o the table of analyses 65 per cent of the samples contained less than 1 per cent of this constituent. Fifteen samples contained small amounts of phosphorus. However, the results further show that it is not impossible to obtain “phosphorus-free” limes. Manganese was found in practically all samples, but generally in extremely small amounts. Manganese apparently affects the color of the lime more than any of the other constituents, giving the samples a grayish tint. As the manganese content decreases the color of the samples becomes lighter. The high-calcium limes were uniformly high in total calcium oxide, indicating that the material was produced from stone carefully selected for chemical lime. Two samples, one hydrate and one quicklime, contained calcium oxide and magnesium oxide in dolomitic proportion. The surfur (SOa) content of the samples varied over a wide range, It has been suggested that the SO3 may be introduced or increased by burning limestone with coal containing sulfur. Lime that is stored may be expected to show some recarbonation, depending upon the method of storage. Where a low carbon dioxide content is desirable, lime should be used as soon as possible after burning. GENERALPHYSICAL CHARACTERISTICS-The quicklime varied from soft. friable materials to hard. dense lumlss. I n a few of the harder quicklimes silica was present as flinty particles approximately l/8 inch in size, easily discernible
CaO 71.51 72.90 73.89 73.45 70.57 98.90 73.10 96.12 70.06 71.54 49.58 58.12 74.41 94.15 77.70 75.09 76.07 96.70 73.51 72.46 73.40 74.45 70.82 72.55 97.50 97.35 73.52 73.26 97.85 71.34 74.22 73.22 72.52 97.24 75.43
MgO 1.56 ND 0.70 0.18 0.11 0.38 0.44 0.36 0.94 0.76 31.05 36.17 0.82 0.95 0.40 0.60 0.18 1.82 0.40 1.24 0.44 0.40 3.88 1.78 0.36 0.36 0.54 0.78 0.22 1.84 0.36 0.80 0.20 0.88 0.25
SOa 1.25 0.27 ND
T
T T 0.48
T T 0.31 0.81 3.33
T T
ND
T
0.87
T 0.11 0.45
T
0.43 0.43 1.68
T
0.95 0.30 0.14
T
1.50 0.24 0.54 0.04 0.84 0.75
co: 1.64 1.19 0.90 0.05 1.60 0.03 0.77 0.28 1.70 0.31 0.71 0.66 1.34 0.04 1.72 0.82 0.24 0.07 0.74 0.67 0.62 0.72 0.66 1.06 0.02 0.04 0.69 0.51 0.26 0.78 0.82 2.04 0.77 2.46 0.67
Loss ON MATTER IN IGNITION 1: 9 HC1 23.50 25.56 23.40 24.52 24.50 0.05 24.34 1.40 24.90 24.20 17.40 0.70 21.80 0.86 15.10 22.80 19.90 0.42 24.22 23.68 24.19 22.70 24.76 21.09 1.60 0.60 23.60 23.54 1.37 23.42 24.06 23.30 25.44 0.60 22.40
0.06 0.44 0.57 0.10 0.86 0.51 0.44 0.04 0.32 0.48 9.55 0.66 0.19 2.77 0.20 0.24 0.87 0.44 0.49 0.23 0.49 0.50 0.44 0.37 0.20 0.55 0.24 0.52 0.16 0.49 0.50 0.70 0.49 0.46 0.43
by visual inspection. Material of this nature would be particularly deleterious to processing machinery, such as piston pumps, etc. Abrasive action holds true for all silica; however, a good share of the SiOz is present in the sample, not as silica but as silicates. The quicklimes varied widely in rate of hydration; some hydrated immediately while others required fully an hour. The color of the quicklimes varied from a chalk-white to a grayish brown. The hydrates were the usual soft, fine, impalpable powders, free from lumps. The hydrates were generally white and with less variation in color than the corresponding quicklimes. Acknowledgment The author wishes to express appreciation to F. W. Smither and R. S. Rudy of the Chemistry Division, Bureau of Standards, for many helpful suggestions which greatly aided in the work.
Report of Food Investigation Board The Department of Scientific and Industrial Research of Great Britain has recently printed the “Report of the Food Investigation Board for the Years 1925, 1926.” The report is divided into two portions: the Report of the Food Investigation Board and the Report of the Director of Food Investigation. Unlike previous reports, the technical summary of the progress of research investigations is not included in the Report of the Food Investigation Board, but instead, in the Report of the Director of Food Investigation. In the former, i t is remarked that increased attention is being paid to industrial problems, thereby necessitating enlarged laboratory facilities. A laboratory has accordingly been established a t Covent Garden Market, in London, to conduct a scientific survey of the conditions of produce after transport and storage, to diagnose the various types of wastage and depreciation, and t o assess their relative importance. The director’s report presents a concise statement of the progress of the investigations carried out under his direction which have not yet reached the stage where full publication of the results obtained is desirable. It covers such subjects as the transportation and storage of numerous foods, studies in freezing, and various papers on c6anges in the apple. The report covers 80 pages and may be procured from His Maiestv’s Stationerv Office. Adastral House.. Kinmwav. _ .W. C. 2 . . London, England, fbr 2 s. 6 d. I
IiVDUSTRIAL AND ENGINEERING CHEMISTRY
October. 1927
1159
Experiments in Wood Preservation‘ 111-Preservative Properties of Basic Substances By Leo Patrick Curtin ENGINEERING LABORATORIES, WESTERN UIION TELEGRAPH Co., A-EW YORK,N. Y.
1925, p r e l i m i n a r y t e s t s were made with sodium carbonate and barium hydroxide which justified this opinion in a c o n c l u s i v e manner.
Sodium Salts ‘Odium is regarded as practically nontoxic toward fungi,2 its kill-
, I t is shown that the fungus Fomes onnosus and probably all other wood-rotting fungi may be inhibited by alkaline, or basic, substances. The fungus normally grows in an acidic environment and is, itself, ordinarily capable of producing the required degree of acidity in its medium of growth. If the basic material is present in concentrations beyond the capacity of the fungus to neutralize, no growth takes place.
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making it difficult to sell. They do not injure m e c h a n i c a l l y , homTeT7er, since the fiber is not attacked. The process of inhibiting the blue stain by sodium and bicarbonate was patented by Cowles4 in 1903. The inventor states that the blue stain is “due
