I44
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
I. The Hibbard method of digestion gives the highest amounts of nitrogen in all cases except one (see Soil No. 3), thus showing a more thorough digestion. 11. The duplicate and triplicate determinations show the best agreement when the Hibbard method is employed. 111. The digestion is carried out most rapidly by the Hibbard method and, particularly, much more rapidly than by the salicylic acid method which, in other respects, comes the nearest to the Hibbard method in yielding satisfactory results. IV. I n all the methods employed, considerable trouble with bumping was experienced except with
litmus paper. The residue was then treated for the digestion of the nitrogen by the different methods whose relative efficiency was to be tested. All the methods given are so well known as to need no further description here. The last method, which was first suggested by Hibbard, as a result of some of his investigations on fertilizers, deserves brief description here, however, since it was published only recently' andcbecause it has given by far the best results in our hands. The method of digestion as proposed by Hibbard consists in treating the substances t o be analyzed with 30 cc. of concentrated H,SO, until fumes of SO, begip to come. off. There is then COMPARISON OF
Method of N determination employed Wilfarth's method..
Gunning-Atterberg method..
NITROGEN DETERMINATIONS BY DIFFERENT METHODS Soil No. 1 soil NO. 2
Time necessary t o clear Nitrogen solution' found Minutes. Mg.
.......................
...............
25
{ 1143
20
Time necessary Per cent. to clear nitrogen solution in humus Minutes
.........................
3.91
30
4.86
4.40
25
5.32
5.89
20
5.57
30 5.44
added 1 2 grams of a salt mixture consisting of I O grams K,SO,, I gram FeSO, and 0.5 gram CuSO,, and the solution is digested until the nitrogen is all changed to ammonia. There follow results obtained by the use of humus portions equivalent in the case of Soil No. I t o I O grams of the soil, in the case of Soil No. 2 t o 1 . 6 6 grams of the soil and in the case of the Soil No. 3 to 0 . 5 gram of the soil. The amounts of nitrogen found in milligrams are given in duplicate or triplicate and the percentages of nitrogen are calculated on the basis of the averages of these amounts. All other data are given in the table below: I n a comparison of the data set forth in the above table, and the experience had in the management of the various determinations we find:
I
40
35
(3.33
Salicylic acid method.. ...........
Soil No. 3
Time necessary Per cent. to clear Nitrogen nitrogen in solution found humus Minutes Mg.
2.31
Hibbard method..
Feb., 1913
5.14
40
6o
{ { {
t
13.27 13.64 13.51 13.05 13.66 13.87 13.94 13.66 13.87 14.28 14.21 14.10
B y JOHNA. SCHAEFFER
The manufacture of sublimed white lead, the commercial name for the basic sulfate of lead prepared by the sublimation process, depends directly upon the oxidation of galena, the sulfide of lead, when subjected to intense heat in an oxidizing atmosphere. The combustion under these conditions proceeds with violence resulting in the formation of a white sublimate, which, when purified, is known as sublimed white lead. THIS JOURNAL, 2, 463. Paper presented at the Eighth International Congress of Applied Chemistry, New York, September, 1912. 1
2
4.62
4.71
4.82
4.95
the Hibbard method, in which ' the digestion proceeded rapidly and quietly in all cases, thus confirming the experience of Hibbard as reported in the paper above cited. V. The manipulation included in the Hibbard method surpasses in simplicity and speed all the other methods tested, among which are those most commonly used to-day. I n view of the fact, therefore, that the Hibbard method is far superior to the others so far as both accuracy and speed are concerned, we must urge its use in all humus nitrogen determinations. SOILSRESEARCH LABORATORY O F CALIFORNIA UNIVERSITY BERKELEY
I
LABORATORY AND PLANT
THE MANUFACTURE AND PROPERTIES OF SUBLIMED WHITE LEAD*
Per cent. nitrogen in humus
The reaction which occurs in this oxidation of galena may be written as follows: 6PbS 1 1 0 , = 2Pb,S,O, 2S0,. This formula, Pb,S,O, or zPbSO,.PbO, is analogous to the generally accepted formula for the basic carbonate of lead--zPbCO,.Pb(OH),. Commercial sublimed white lead, however, contains a higher percentage of lead sulfate than that required for the above theoretical formula. While the formation of the theoretical basic sulfate of lead is entirely feasible, its manufacture has not proved commercially advantageous. The conditions for the oxidation of the sulfide of lead are, consequently, so adjusted that a compound showing about 16 per cent. of lead oxide is ob-
+
+
Feb., ~
9
~ T3 H E .JOliRS.4L OF 1iVDUSTRIAL A N D E!VGIA'EERI.YG C - I I E M I S T RY
tained. The conversion of a small percentage of the lead oxide, present in the theoretical basic sulfate of lead, to lead sulfate, undoubtedly results from a reaction between the lead oxide and the sulfur trioxide which forms from the oxidation of a certain amount of sulfur dioxide. A small percentage of zinc oxide is formed a t the same time from the sphalerite, the sulfide of zinc, which is present in almost all nonargentiferous lcad ores. I t is maintained that the presence of about 6 per cent. of zinc oxide enhances the value of the pigment. Coke of a hard compact variety is used as fuel, while iron, in the metallic form, and limestone serve as fluxing materials together with the silica present in the ore. Any metallic lead which forms from a reduction of the lead compounds by the coke, a t the intense heat continually maintained in the furnace, is separated from the readily fusible slag by a difference in their specific gravities.
745
front n.hich serves as a tap holc for the continuous removal of slag and metallic lead and their scparation by the difference in their specific gravities. An oxidizing atmosphere is maintained by blowing air through tuyPre boles entering near the base of the furnace. The feed door of suitable size and form is placed a t one side of the furnaces. The brickwork surrounding the water-jacket or furnace proper is extended upward so as to form a large combustion chamber, which is in some cases water-jacketed. Immediately upon feeding the charge into the furnace, the fire of which is maintained at a point of incandescence, the reactions previously described occur with great violence and the volatilized lead passes upward into the combustion chamber. Suction is maintained by a powcrful fan placed between the bag room and the "goose-necks" which draws the condensed fume onward through the c o o l i n g system, finally driving i t into the hag room where i t is deposited. The cooling system is built so as to produce maximum cooling effect by the introduction of baffles which prevent the casy passage of the fumes into the bag room. After RIINOEMBNI- O F RAG E O O S the fume has passed out F16. I- DIAGXAM SILONINe L O C h l l O N 07 PTIRNdCBS 1N BZX,&zmN of the beehive. where it isi condensed and ourified. it is TO COMBUSTION C H A M I B R AND ''BEBNZY6'' drawn through the "goose-necks,'' large inverted Blue Fume, the fume known commercially as sub- U-shaped pipes resting on hoppers, by the large suclimed blue lead, is frequently added to the charge. tion fans and thence forced into the bag room. This fume is formed in the smelting of lead ores and The bag room is of a special type somewhat similar is recovered by the bag room process. I t is found to to those used in the collection of all fumes. contain about 35 per cent. of lead oxide and about 50 In the sublimed white lead bag room, however, are per cent. of lead sulfate. This fume pigment, sub- found three rows of hoppers (Fig. V), each hopper limed blue lead, is rapidly finding extended use as a carrying 24 bags. The pressure of the fan forces all paint pigment for the protection of iron and steel. the gas through the cloth of the bags, while the subliIts composition renders it extremely valuable as mate is deposited. Occasional shaking throws the charge material and being a product of sublimation i t is fume into the hopper where i t is packed for shipment. extremely reactive when subjected to the conditions Sublimed white lead, as it is removed from the found in the oxidizing furnaces. hoppers, is white in color. Much fume, however, The method of charging the furnaces varies with which is unsatisfactory and not suited for use in the atmospheric conditions and the life and temperature various arts, is deposited in the portion of the cooling of the furnace, charges being formulated to meet system preceding the suction fan. This fume is conthese conditions. taminated with a small percentage of coke, ash and By following the charge from the raw materials to other impurities, and being of a higher specific gravity the finished products, the general working conditions than pure sublimed white lead it is readily deposited before reaching the fan, by a careful adjustment of can he best understood. The oxidizing furnaces, two being considered a the suction. The fume becomes darker in color the unit, consist of oval iron water-jackets, four feet in nearer the approach to the furnace. As a charge maheight, open at both ends, the upper end being five terial the sublimate is excellent, owing to its ve'ry finely divided condition. feet in length and three and one-half feet in width. Sublimed white lead, being a fume product, conThis water-jacket is securely built in a brick structure, on a solid brick base. and has a small opening in sists of very fine amorphous particles, in size about
T H E ~OL~R.\-ALOF I-YD C S T R I A L L 4 AE-YGI~YEERI-YG ~ ~ CHEXISTRY
Feb., 1913
Feb., 1913
T H E J O U R N A L OF I N D U S T R I A L A N D HEGINEERING C H E M I S T R Y
one thirty-five thousandth of an inch in diameter. I t s specific gravity is found to be 6 . 2 . In composition it shows approximately 78 per cent. of lead sulfate, 16 per cent. of lead oxide, and 5 . 5 per cent. of zinc oxide. That the lead oxide present is chemically combined as a basic sulfate of lead, the sulfate of lead present in excess of the amount required for the theoretical formula being present as neutral sulfate of lead, is held by practically all authorities. Chevalier claims the formula of Pb,S,O, for the fume resulting from a furnace roasting lead sulfide. According to Toch,I we find that “ A mixture of precipitated lead sulfate, litharge and zinc white in approximately the proportions found in sublimed
FIG.\‘-HOPPERS
I47
est difficulty. It shows only slight darkening in an atmosphere containing appreciable amounts of hydrogen sulfide gas. When used in colored paints containing chemically reactive tinting materials, it exhibits chemical inertness. The tinctorial power and opacity is directly lowered with a decrease in the percentage of lead oxide. When chalking is noted in paints containing high percentages of sublimed white lead, it is found to differ from that noted in the case of other white lead pigments. According to Holley,~ we find: “When ordinary white lead begins to chalk vigorously, it will be found that the paint film has lost its elasticity, and has become brittle and friable throughout; also,
INTO WHICH SUBLIMED WHITE LEAD FALLS FROM BAG ROOM
lead, when ground in oil and reduced to the proper consistency, dries totally different from sublimed white lead ; in fact, sublimed white lead, when ground in raw linseed oil, takes two days to dry dust free, but the mixture just cited will dry sufficiently hard for repainting in twelve hours, because lead sulfate is a fair drier and lead oxide a powerful one. The oxysulfate having the same composition, behaves totally different from the mixture.” A mixture of the neutral lead sulfate with two per cent. of sublimed litharge, the finest and palest oxide of lead yet prepared, shows a yellow color not approached by any sublimed white lead yet made. When sublimed white lead is subjected to the heat of the blowpipe it is reduced to metallic lead, when intimately mixed with charcoal only with the great“Chemipy and Technology of Mixed Paints,” Maximilian Toch, p. 19.
that the luster of the film under the chalk-like coating has entirely disappeared. A sublimed white lead film, on the other hand, retains much of its original elasticity under the chalk coating, indicating that the disintegration is confined to the surface, and i t is possible that the retention of the ‘chalk’ on the surface gives some protection to the unaffected coat below.” The pigment, in common with other white lead compounds, finds its greatest value when compounded with zinc oxide and a small percentage of inert pigment of a crystalline nature, as these pigments tend to overcome those factors which militate against the use of the pigment alone. Sublimed white lead is a pigment extensively used in the compounding of the finer grades of rubber goods. 1
“ Z i n c and Lead Pigments,” Holley, p. 115.
T I I E JOVRIVAL OF IiX'DlJ5I'RIAL AhTD En'GlNEERISG CHE.UI.YTR 1.
148
The pigment has been found t o practically inhibit corrosion on iron and stcel even after long exposures, and ranks favorably with all other pigments yet prepared for the elimination of this decay. I n consequence, i t is rapidly finding its predicted place among paint pigments not only as a protective coating for wood but as a preservative for iron and steel. I'ICXER
LE*D C". Mu.
JOPLIN,
AiTEWFORMOFLABORATORYEXTRACTIOAAPPARATUS'
Feb., 1 9 1 3
have resulted in the construction of the form of apparatus which is here described. The frame supporting the apparatus (Fig. I ) is of x / % inch metal tubing and bas approximate dimensions of 36 X 3 2 X 8 inches, accommodating 8 extraction flasks which are placed 3'/% inches between centers. The extraction flask A (Fig. 3 ) is flat bottomed inches and a height of and has a diameter of 2 inches to the base of the neck; the constricted portion of the neck B has height and diameter of about
B Y A. E. P ~ n ~ r r s Received October 2 5 , 1912
The great variety of extraction apparatus now on the market would seem a t first thought t o supply a form adapted to any purpose; yet, in selecting apparatus for continuous use in a laboratory where large numbers of extractions must be made, one is impressed with the fact that all these forms have in common some of the disadvantages enumerated below. Most forms of extraction apparatus are very complicated, very expensive and very frail. Nearly all forms have two joints of the cork, ground glass or mercury seal type. These are sources of endless breakage trouble and annoyance, besides furnishing an
I I'IZ.
2
one-half inch each; the large upper portion of the neck C:has a diameter of I ' / ~ inches and a height of 1 2 inches. The condenser D is merely a test tube of special shape (9 inches x inch). The small glass tube E has a diameter of about 3 / 1 8 inch. All glass parts are of rather heavy German glass. The dimensions will accommodate any extraction tube up t o 5 inches in length and one inch in diameter. A perforated porcelain, or aluminum plate is used t o support tubes of small size. The box F (Fig. I ) , enclosing the lower part of the extraction flask, is of sheet metal about 4 inches high, the front, back and top bcing hinged so that they can he dropped out of the way, leaving the bottom of the box as an open platform vhcn the flasks are being adjusted. The bottom 01 this box has an opening, G, three inches wide and extending the cntire length of the box, except for two inches a t either end. Heat is supplied by stcam passing through a r/, inch lead 12iG. 1 pipe, H, which makes three circuits of the box, being easy means of contaminating sample or solvent with separated from the bottom by a layer of asbestos water leaking from or condensing on the supply pipes. hoard. The valve controlling the flow of steam is Tiearly all the common forms of extraction apparatus not shown in the drawing. The I/, inch lead pipe must be supplied with water under pressure, which carrying the exhaust steam enters the waste pipe must ordinarily be conveyed to the condenser through through a Tee joint, J , and extends downward 4 or rubher tubing. This rubher tubing may irequently 5 feet, completely condensing the exhaust steam. break or leak and flood the laboratory, or kink and The extraction flask when in position is supported shut off the water supply; moreover, t o keep it in good directly over the opening G by a strip of heavy sheet condition requires continual care and expense. copper 3 X 7 inches in dimensions, the ends of which Efforts by the writer to eliminate ccrtain of these rest on the steam heating coil, the copper strip serving defects from a n apparatusto he used in this laboratory also to conduct heat to the Bask. When the Bask 1 Drawings by Mr. Wm. P. Beechinn. Jr. is being put into or taken out of position, the copper
