June. 1927
ISDL7STRI.4L -4-1-D E-YGIXEERISG CHEMISTRY
honey mixture is superior to a calcium arsenate-molasses mixture containing the same amount of calcium arsenate. 11-Unfavorable weather and crop condit>ionsmade it impossible t o make trustworthy comparisons of t'he relative effectiveness of the fluosilicates, the special calcium arsenate, and commercial calcium arsenate from the one-acre plot tests made t o date. ,411 these materials showed definite weevil control and there was no plant injury apparent on field cott'on in any case. It is hoped to establish the relative effectiveness of these materials during the present year. 12-There is little hope of poisoning the boll weevil in the field by t,he use of yolatile gases. 13-The following are various estimates pertaining to the weevil : Average weight of a boll weevii (does not include undersized weevils) .4mount of air breathed by a boll weevil per hour Minimum arsenic required t o kill a boll weevil Average arsenic content found in weevils killed with calcium arsenate Amount of water a weevil drinks per d a y
15 0 mp.
0 33 cc. 0 (10013 m::
'I
0 , (102 mg. 0 . 0 2 cc.
Possibly too high.
14-1-0 substances were found which definitely attracted or repelled t'he boll weevil. X o substances were found which irritated the weevil sufficiently to make it fly. 15-In carrying out the directions of the Association of Southern Agricultural Workers and the Department of Agriculture for boll weevil control, the following suggestion is made: When t.he initial weevil infestation is below twenty weevils per acre or when it is, or has been, reduced to local infestation, the fight should be continued against t,he individual weevils both by local poisoning and by picking up
ill
the f a l l ~ npunctured squares locally, a b neceasary, to insure the most complete control possible. Advanced cotton and badly infested cotton should receive special attention in order to prevent multiplication of the weevils in these local spots and later infestation of the entire crop. Success in the fight against overwintered weevils will gire complete security against any large amount of weevil damage. Acknowledgment
The Chemical Warfare Service desires to express its appreciation of the assistance and cooperation of the U. S. Department of Agriculture and the various state experiment stations, and especially of the facilities furnished by the respectire experiment stations of Georgia, Florida, and South Carolina for this work. I n addition to these facilities, we received the heartiest personal cooperation from these sources. H. P. Stuckey, director of the Georgia Experiment Station; Wilmon Kewell, director of the State Plant Board of Florida; and H. W.Barre, director of the South Carolina Experiment Station, on all occasions cooperated with the Chemical Warfare Service to the fullest extent. T o il. F. Camp, botanist, Florida Experiment Station. B. B. Higgins. botanist, and R. P. Bledsoe, agronomist, Georgia Experiment Station, we express our appreciation for the many services rendered. I t should be stated that the field tests on the one-acre plots at the Georgia E-qeriment Station and vicinity were carried out with N r . Bledsoe's direction, cooperation, and personal supervision. The assistance of Miss Naomi Chapman, of the Georgia Experiment Station, and of E. F. Grossman and P.W.Calhouc, of the Florida Experiment Station, is gratefully acknowledged.
Lime for the Glass Industry' By Edwin P. Arthur DEPARTMEST OF C H E M I C AENGINEERING, L T H EOHIO STATEUNIVERSITY, COLUMBUS, OHIO
ESY than 2 per cent of the total lime production of the Vnited States is consumed in the manufacture of glass.? "eyertheless, many lime producers find the glass trade attractive. The demand is less subject to fluctuations than building construction. The business, even though small in amount, is especially welcome during dull seasons. For approximate calculations it is permissible to assume that glass will contain 10 per cent lime. Thus, if a glass factory produces 50 tons of glass per day, the lime requirement will be about 5 tons per day or one minimum carload per week. Somewhat more than 10 per cent lime is used in flat glass and generally less in hollow mare. Soda ash is largely used t o furnish the alkali for ordinary soda-lime glass. Thirty per cent of the soda ash produced in the United States is used in the glass business, amounting in 1925 to 520,000 tons.3 Estimating average glass to contain 15 per cent of Piano, the total production of glass is indicated as 2 million tons
L
with a consequent lime requirement of 200,000 tons annually. Since present consumption of lime is less than 75,000 tons, it may be seen at once that considerably less than half the Received M a y 2, 1927. Willis, Chem. 6' Met. E n g . , 33, 7 6 3 (1926), quotes Bureau of Mines, "Lime in 1924," figures for lime sold by producers t o glass works a s 1.8 per cent of t h e total or 72,822tons. 3 Chem. &' M e f . Eng.. 33, 49 (1926). 2
glass is made from burned lime, the raw ground stone being used instead. (Allowance is not made for special glasses which require soda ash but no lime.) Burned lime is generally more expensive than raw limestone as a raw material for glass-making per ton of available material delirered for melting.4 But since the raw material cost of glassware is often only 10 to 20 per cent of the total, a small improvement in quality by use of burned lime would more than offset its increased cost. Apparently no definite information on the relative merits of lime and limestone is available in the literature. It has been stated5 that plate glass made with lime is as good but no better than that made from raw stone. When raw stone of excellent quality from the same deposit is substituted for burned lime in the manufacture of window glass, no appreciable difference in operation has been noticed either in fuel requirements or in quality of glass produced. It is, of course, obviously unfair to make comparison of lime and stone of entirely different character, as, for example, a burned dolomite and high-calcium limestone. There is, however, much to recommend burned lime. It is subject to more careful inspection than raw stone. It will generally be more uniform chemically and less contaminated with incidental impurities. A batch mixed with lime occupies less space per unit weight and consequently more material can be held in the melting area of a large tank furnace. 4 6
Arthur, J. A m Cer. SOC.,8, 126 (1925). h d a m s , Glass I n d , 8, 2 (1927).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
712
Even though no more or better glass is delivered by a furnace using a burned-lime batch, nevertheless, the fact that the batch can be held closer to the “back end” of the furnace affords a welcome factor of safety to the glass maker, especially if the furnace is operating near capacity. Chemically the most important item is iron content because of the green color which iron imparts to glass. Firstclass lime for glass-making should contain less than 0.2 per cent iron oxide.6 The question of iron content is becoming increasingly important. Glass sand is being produced containing 0.02 per cent Fez03. I n a glass which is 75 per cent SiOz and 10 per cent CaO-MgO, sand furnishes less iron to the glass than lime if the lime contains more than 0.15 per cent Fez03. The table ware and hollow ware branches of the industry are forced to seek low-iron sources of lime in order to make the brilliant water-white glass demanded. It is said that some market is being found for precipitated calcium carbonate of low iron content a t substantially higher prices than lime. 8
Williams, Bzw. Standards, Circ. 118.
Vol. 19, No. 6
Lime for the glass trade should be slightly overburned. Off-color lime which might be unsuitable for building purposes would be quite acceptable for glass-making. Overburned lime does not hydrate so readily-a decided advantage in shipment and storage. Lime in the open storage bin of a glass factory on a river bank has been found to absorb as much as 9 per cent HzO in 10 days. If reserve stocks of lime at a glass works can be kept in air-tight steel drums, using each shipment of lime as received, a uniform batch can be assured. Little or no effort has been made by lime producers to furnish glass makers with a product adapted mechanically to the process of glass manufacture. The ordinary finishing lime is so finely ground that it is difficult to handle in mixing and conveying machinery. Lime dust blown from batch in the furnace has a tendency t o clog furnace flues and regenerators. It would appear desirable for lime producers to make a companion product for the “dense dustless” soda ash now in universal use. Tailings, screenings, and rejects from an air separator might be recovered as an ideal product for glass-making.
Lime for the Absorption of Chlorine in Paper Mill “Bleach Liquor” Practice’ By A. H. Hooker, Sr. HOOKER ELECTROCHEMICAL Co., NIAGARA FALLS, N. Y.
I
N SELECTIKG a lime for the absorption of chlorine we consider the production of either dry “bleaching powder” or liquid bleach. By far the largest use for these two products is in the paper mills. Until quite recently chlorine was nearly always purchased by the paper mills in the form of bleaching powder; consequently, the lime used to absorb the chlorine was purchased and hydrated by the manufacturer of chlorine. A very radical change has taken place, however, and the use of bleaching powder has been rapidly displaced by the use of liquid chlorine and the purchase by the paper mills of hydrated lime, in 50pound bags, or burned lime hydrated a t the mill and the absorption of chlorine in a milk-of-lime suspension. The ultimate aim in the paper mill, whether using bleaching powder or liquid chlorine and milk of lime, is to obtain the chlorine in the form of a solution of calcium hypochlorite plus calcium chloride, together with a small amount of free soluble lime and in a clean solution. Such solutions are invariably prepared by decantation and generally with a return counter wash so as to obtain all the values possible from the sludge. One must understand this operation clearly before he can decide on the qualities of the lime most suited to his use. Preparation of Bleach Solution from Bleaching Powder
Let us consider first the preparation of a typical bleach solution from bleaching powder. This lime must first be hydrated in a mechanical hydrator. It is then spread in layers a few inches thick on the floor of a bleaching chamber or handled in a mechanical bleach machine. Chlorine is absorbed to a point where there will be present about 38 1 Presented under the title “Importance of the Proper Lime in the Use of Liquid Chleri-ne for Breaching. and Sterilization” as a part of the Lime Symposium before the Division of Industrial and Engineering Chemistry a t the 73rd Meeting of the American Chemical Society, Richmond, Va., April 11 to 16, 1927.
per cent of total chlorine and 62 per cent of hydrated lime, excess moisture, and impurities. Not more than 80 per cent of the actual lime present is combined with the chlorine, a n excess of about 20 per cent being required to “stabilize” the bleach. When this bleach is received by the consumer it must be dissolved and made into clear solution for use. Such bleach solutions usually contain from 21 to 42 grams of available chlorine per liter, 21 grams equal one-half pound of 35 per cent bleach per gallon. Let us take a typical solution containing in its finished state about 0.8 pound of 35 per cent bleach per gallon, equal to 33.6 grams of available chlorine per liter. Assuming that we have two tanks each 10 feet deep and 10 feet square equipped with agitators, these tanks will have a capacity of 1000 cubic feet, or 7500 gallons, each and can be operated on the counter-wash system. A drum of bleach will weigh about 750 pounds. One drum will therefore correspond to 0.1 pound of bleach per gallon. If we add six dryms of bleach a t about 25” C. (77” F.), mix this bleach for about 15 minutes, and allow it to settle, we will find that with a good quality of bleach we have a t the end of 2 hours 30.5 per cent of sludge, 3 hours 21.6, 4 hours 19, 5 hours 17, 10 hours 13 per cent, or 1.3 feet of actual sludge. If we mixed this bleach with colder water or if it was made with lime which did not settle so well, the volumes of sludge over this same period of time would be materially increased. The same would be equally true, of course, if we added more bleaching powder. With the same quality of bleach and the same amount added but with a difference of mixing it a t 15” C. (59” F.) we would have at the end of 2 hours 47 per cent of sludge, 3 hours 35.75, 4 hours 29, 5 hours 22.25, and 10 hours 18.75 per cent of sludge. This is the actual sludge in the tank. I n addition to this, in decanting the clear liquor, there is always left a certain amount above the sludge, 4 inches equal to 3.3 per cent on a 10-foot tank, which must be added to the above sludges. We would
,
