T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
I j6
a n d t h e iodine titration i n both Test B a n d Test C indicates t h a t t h e methods are reliable when applied t o solutions of hydrogen sulfide. I n fact t h e y made a better recovery of t h e hydrogen sulfide t h a n t h e direct titration method, b y t h e ratio of about I O O t o 88. TABLEIV-TESTS
ON
AQUEOUS HYDROGEN SULFIDE Reaction ................ Iodine
Procedure A-Into a 500 cc. Erlenmeyer flask containing 250 cc. water were poured from a cylinder 50 cc. of sample, starch added, and the liquid titrated at once.. .................... B-Into a 500 cc. Erlenmever. neutral tet-
figure
9.06
NaOH were introduced, followed by Stood three minutes before titration.. . . . . . . . . . . . . IO. 22 repetition of B, except stood 6 minutes before titration.. . . . . . . . . . . . . 10.09 repetition of A , , . . . . . . . . . . . . . . . . 50 cc. of sample.
C-A D-A
titration
10.29
10.05 8.72
Moreover, t h e iodine titration of t h e thiosulfate progresses decidedly more smoothly, rapidly a n d with a sharper end-point t h a n t h e iodine titration of t h e original hydrogen sulfide. T h e method accordingly seems t o offer promise in certain other estimations of soluble sulfides or hydrogen sulfide. 5. METHOD C FOR S U L F I D E - A C I D FIGURE-The Sample was a diluted proprietary preparation. The' factor for t h e thiosulfate solution against t h e N / I iodine was found t o be 0 . 9 9 7 ; therefore t h e factor for t h e tetrathionate solution was 0.499 X N / I o . TABLEV-COXPARISOXOF SULFIDE-ACID FIGURESB Y METHODB AND METHODC IV V I I1 I11 Total Figure by TetraFigure by iodine Thiosulfate Method thionate Method C Test No. titration titration B(1-11) titration (IV X 0.499)
..........
1 23.82 2 . . . . . . . . . . 23.79
Mean,
23.81
0.98 0.98 0.98
.....
45.5-45.7 45.5-45.7
..... .....
22.83
45.6$0.2 = 45.8
22.85
.....
An a t t e m p t was made t o determine directly t h e 'cortion for end-point t h u s : T o I O cc. of dilute ammonia ( I : 9 ) i n a 100 cc. beaker was added from a capillary pipette 0.I O cc. of t h e same lime-sulfur solution; t h e n 50 cc. distilled water were run in from a burette a s in titration. The clear liquid was distinctly yellow a n d gave a plain positive test with nickel sulfate. There was t h e n added 0 . 2 0 cc. of N / 2 0 tetrathionate, after mThich a test with nickel sulfate yielded a positive result, b u t so faint t h a t it is questionable whether i t would have been detected in presence of t h e usual
Vol. 8 , No. z
amount of precipitated sulfur. After addition of 0 . 4 cc. tetrathionate t h e test with nickel sulfate was negative. A repetition gave a n identical result. T h e theoretical titration would, of course, be 0 . 4 6 cc. It seems therefore t h a t a correction of about 0 .2 cc. N / 2 0 tetrathionate may fairly be added t o compensate for insensitiveness of indicator a n d slight oxidation which must necessarily result from the action of t h e air during titration. Though Table V showed excellent results for Method C, there still remained t h e possibility t h a t t h e method might not be trustworthy for solutions containing a n excess of lime on account of possible appreciable decomposition of tetrathionate in alkaline solution before reaction with sulfide h a d gone t o completion. Therefore I O cc. portions of a lime-sulfur solution were titrated with tetrathionate after being diluted as follows: ( a ) with I O cc. dilute ammonia, as in t h e regular method, ( b ) with I O cc. concentrated ammonia, (c) with I O cc. N / I O X a O H a n d I cc. concentrated a m monia. Several repetitions of t h e titrations gave exactly t h e same result for all, namely, a n end-point between 5 2 . 5 a n d j ~ 7 . cc. standard tetrathionate. Evidently t h e titration is entirely trustworthy when carried out on solutions strongly alkaline with ammonia, ~ or alkaline t o saturation with calcium hydroxide, t h e conditions produced under (c). CONCLUSIONS
The methods described appear scientifically sound, being based on definite reactions and-assuming the absence of sulfites-involving no significant errors of which t h e source a n d probable magnitude cannot be estimated. They also appear practically applicable for use in t h e laboratory, some of t h e m affording t h e desired information even for dirty dipping baths through which cattle a n d sheep have passed. T h e operations, though perhaps appearing numerous a t first sight, are simple a n d rapidly executed when once t h e procedure has been grasped, while t h e s t a n d a r d solutions required are only those commonly a t h a n d in all laboratories. Some of t h e methods appear t o offer promise for t h e determination of hydrogen sulfide or compounds thereof in other materials. BIOCHEXIC DIVISION, BUREAU OF ANIMAL Ih-DUSTRY U. s DEPARTXENT OF AGRICULTURE WASHINGTOS
LABORATORY AND PLANT THE PRODUCTION OF AMMONIA FROM CYANAMID' By W. S. LANDIS INTRODUCTION
After working for many years on t h e problem of t h e fixation of atmospheric nitrogen i n t h e form of cyanides a n d cyanamides, t h e outbreak of t h e Boer War forced Professors F r a n k a n d Caro of Berlin t o t u r n their attention t o t h e utilization of their products otherwise t h a n in t h e field of precious metal extraction. A consequence of t h e t h e n existing economic situation was t h e discovery of t h e process of transforming t h e 1 Presented at 8th Annual Meeting of the American Institute of Chemical Engineers, January 12, 1916, Baltimore, Maryland.
cyanamide compounds into ammonia. United States P a t e n t No. 776,314, granted November 29, 1904, most probably represents t h e first American publication on this subject. According t o t h e specifications of this patent various cyanamide compounds a n d derivatives, including t h e crude form of t h e calcium salt sold under t h e name of Lime Nitrogen, when treated with steam or water in t h e proportion of three molecules of water t o t w o atoms of t h e nitrogen in t h e cyanamide salt, will yield ammonia. I t is recommended in t h e specifications t h a t t h e reaction be carried out a t temperatures from
Feb.,
1916
I
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
160-180’ C. i n a closed vessel, though t h e claims of this patent cover temperatures above 100’ C. There has grown around this process a n d its later refinements in t h e last fifteen years a n extremely important ammonia industry. Naturally t h e greatest development has been in Europe, its home, a n d i t is only within t h e past year t h a t a plant comprising fullsized a p p a r a t u s has been in operation in t h e United States. I n attempting t o catalog t h e various p l a n t s , throughout t h e world which have been converting cyanamid into ammonia i n large scale operations, I find t h a t available information, particularly since t h e outbreak of t h e European War, is so incomplete t h a t t h e listing in consequence was very inaccurate. It is certain, however, t h a t t h e transformation of cyanamid into ammonia is successfully carried out in Norway, Germany, France, Switzerland, I t a l y a n d Japan, a n d , prior t o t h e war, in Belgium, the bulk of t h e product going into ammonium sulfate for t h e chemical a n d fertilizer trade. Norway is producing large quantities of ammonia used i n t h e Birkeland-Eyde plants for t h e production of ammonium nitrate; France has produced considerable quantities of anhydrous ammonia b y this process; a t t h e present time Germany is producing enormous quantities of nitric acid from this cyanamidammonia b y a newly developed oxidation process, a n d is erecting cyanamid plants equipped with ammonia apparatus a t various places. T h e fixation of atmospheric nitrogen, chiefly due t o our Government’s policy i n respect t o water power development, has not been practiced in t h e United States. During t h e year 1914 contracts were let in Germany by t h e American Cyanamid Company for t h e equipment of t h e largest single ‘ammonia plant t h e n projected or operating i n t h e cyanamid industry, b u t t h e outbreak of t h e European war interfered with t h e shipment of this apparatus, nearly all of which was seized b y t h e German Government for t h e purpose of providing for its own explosive requirements. I t was possible t o bring only a small portion of this equipment over t o t h e States, where it was set u p a n d p u t into operation, a n d is now producing several tons of pure ammonia gas per d a y . This plant has been in continuous operation here for six months without a n y signs of trouble whatever a n d is considered t o be most successful a n d satisfactory in every way. R A W MATERIALS
T h e crude Cyanamid or Lime Nitrogen is now a well known commercial product. T h e Canadian factory supplying t h e United States a n d its insular possessions with this product has a capacity of fixing nitrogen equivalent t o 90,000 lbs. of ammonia per d a y , a n d with t h e completion of certain additions now being made will be capable of supplying some 110,000 lbs. of ammonia each 24 hours. T h e demands for this product, most of which goes into t h e fertilizer industry, are so great t h a t t h e plant is now operating a t its full rated capacity. It is therefore evident t h a t t h e supply of raw material for a n ammonia industry is i n no sense limit e d , Crude Cyanamid or Lime Nitrogen, t h e reagent used
IS7
for t h e production of ammonia, is a n electric furnace product, whose production has been described elsewhere b y t h e writer.’ This material a s turned o u t of t h e furnace contains nearly z j per cent nitrogen in t h e form of CaCN2, 1 2 per cent CaO a n d 1 2 per cent carbon, with miscellaneous impurities derived from t h e various raw materials entering into i t s manufacture. T h e other raw materials entering into t h e ammonia process are soda ash a n d hydrated lime. T h e quantities used are small, being approximately, 3.5 a n d 2 per cent respectively of t h e weight of Lime Nitrogen used. Steam a n d power requirements, which v a r y with t h e size of t h e plant, are discussed later. CHEMISTRY
On treating Lime Nitrogen with steam, ammonia i s produced from t h e calcium cyanamide according to t h e following reaction: CaCNz 3H,O = CaC03 2NH3. The reSction is almost quantitative when carried out on a large scale according t o t h e process t o be described later in detail. This reaction is exothermic in character, a n d while t h e exact heat of formation of calcium cyanamide has never been determined accurately i t is believed t h a t t h e heat evolution from t h e decomposition of t h e cyanamide alone amounts t o between 200 a n d 300 lbs. cals. per pound of ammonia evolved. This plays a n important part in t h e present method of carrying out t h e process, inasmuch as after once starting t h e reaction under proper conditions i t will proceed of itself, a n d , in fact, with such great velocity t h a t only complicated a n d highly developed apparatus can t a k e care of t h e gaseous products. T h e process as carried out in t h e plant operating in t h e United States is essentially t h a t described in t h e specifications of United States P a t e n t 1,149,633, dated August I O , 191 j, “Process of Making Ammonia from Calcium Cyanamid.” I n order t o t a k e advantage of t h e exothermic character of t h e reaction, as above s t a t e d , t h e process is made t o take place in a n autoclave partly under high pressure. This apparatus consists of a steel t a n k approximately 6 ft. in diameter, 2 1 f t . high a n d capable of operating under a working pressure of 3 0 0 lbs. per sq. in. It is provided with a powerful stirring apparatus. I n t o this autoclave is charged about 1 2 , 0 0 0 lbs. of mother liquor derived from a previous operation (fresh water t o s t a r t ) , a n d Lime Nitrogen is slowly fed into this liquor under continuous agitation. As t h e Lime Nitrogen contains always a fraction of a per cent of undecomposed carbid, acetylene is evolved during this dissolving of t h e Lime Nitrogen. A proper ventilating system is provided t o remove this acetylene at such dilutions as will be non-explosive even if subjected t o a source of ignition. The charging is usually carried on over a period of a n hour so as t o insure a thorough incorporation of t h e Lime Nitrogen with t h e solution a n d t h e breaking u p of all lumps in t h e slurry. When t h e Lime Nitrogen has all been added t o t h e autoclave t h e reagents-soda and lime-are added
+
1
THISJOWRIAL. 7
(1915), 433
+
T H E J O C R S A L OF I N D C S T R I A L A N D ESGINEERIATG CHEMISTRY
Ij8
for the purpose of increasing t h e efficiency of ammonia evolution. principally through prevention of t h e formation of polymeric forms of cyanamide compounds which are difficult of transformation into ammonia. The autoclal-e is then closed 2nd steam is admitted €or approximately I; minutes. or until t h e pressure gauge on t h e autoclave registers 3 or 4 atmospheres, which indicates t h a t t h e temperature in the autoclave 60 I I I I
I
Hrs.
0
2
/ FIG.
3
4
I
has been raised sufficiently t o s t a r t t h e reaction a t a fair rate of speed. The reaction then proceeds of itself, generating ammonia and steam in the autoclave, and it IS necessary t o relieve this gas accumulation, by means of suitable valves, t o avoid excessive pressures in the apparatus. The rate of reaction becomes cumulative as the temperature rises, and this relief of ammonia and steam must be permitted. Gnder normal working conditions t h e pressure in t h e autoclave will rise t o about 12-15 atmospheres in the course of about 2 0 minutes. with the relief valre open. The pressure then drops o f f slowly, as the gas is discharged, t h e rate of discharge being usually regulated by t h e attendant a t t h e valve so as t o maintain a constant pressure in t h e ammonia line, and a t t h e end of about one and 2 half hours from the s t a r t of t h e operation t h e evolution has usually stopped. Nearly all of t h e cyanamide in the charge has been decomposed during this first period of t h e operation, b u t t h e solution is still highly charged with ammonia, which it is necessary t o expel. A very small amount of undecomposed Lime Nitrogen may be left, particularly of polymerized forms, which yield u p ammonia only slowly. T h e steaming operation is then repeated, this time introducing steam until t h e pressure of t h e autoclave goes u p t o 6-8 atmospheres. The ammonia discharge valves are again opened until the autoclave is discharged, requiring a period averaging approximately one-half hour for this second discharge. I n order t o insure practically complete evolution of all t h e ammonia in the autoclave it is advisable t o again repeat t h e steaming t o 6-8 atmospheres for a third period, discharging as before. During this last period of steaming and discharge rarely over z per cent of t h e total ammonia as charged is evolved, and it can, therefore, be omitted if extraordinary demands on t h e capacity of t h e apparatus are made.
Tol. 8. KO.2
Extended studies of the course of this decomposition of Lime Nitrogen in the autoclave have been made both abroad and in this country, and are here reproduced in the form of charts. T h e discharge from t h e autoclave consists of a mixture of steam and ammonia, t h e composition progressively changing during t h e cycle. This variation in composition is shown for a n actual operation carried out in this country in Fig. I , in which t h e ordinates represent t h e percentage of NH3 by weight in the ammonia-steam mixture discharged from the autoclaves, and the abscissa t h e time after start of the operation, analyses of discharge being made a t approximately three-minute intervals. The rate a t which ammonia is discharged from the autoclave under operating conditions varies with t h e imposed condition. I t has been found t h a t most requirements are met b y discharging a t such rate a s t o maintain a constant pressure of steam and ammonia in the main leading f r o m the autoclave. Under such conditions the rates of discharge during a given operating cycle are represented b y t h e curve in Fig. 2 , in which t h e ordinates are the pounds of ammonia dis-. charged per hour, and the abscissa again t h e various elapsed times from the start. I n this case the charge in the autoclave was 7 0 0 0 Ibs. of Lime Sitrogen analyzing about 2 6 per cent equivalent “3. Where a uniform supply of ammonia is required it can be obtained b y the insertion of a special t y p e of gasometer in t h e system. Also suitable grouping of a number of autoclaves and cyclical operation of t h e same will assist greatly in obtaining a uniform rate of production without t h e use of such gasometer. I n Fig. 3 is shown a curve of t h e pressures existing in a n European autoclave, slightly smaller t h a n t h e one described above, and operating on a charge of 8000 lbs. of Lime Nitrogen. T h e dotted lines represent
FIG.2
t h e admission of steam, and the full lines t h e pressures as s h o ~ v non t h e gauge on t h e autoclave. The ammonia discharge valves of t h e autoclaves are opened where t h e lines are indicated double. At t h e close of t h e operation t h e bottom discharge valve is opened,and t h e mud contained therein runs b y gravity into large suction filters of the well known “Nutsche” type. Here t h e liquor is sucked off from the solid constituents, a thorough wash with water is given and the sludge removed t o t h e dump. Under
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING C H E X I S T R Y
Feb., 1916
normal operating conditions this sludge when dried contains less t h a n 0.2 per cent of equivalent ammonia, and about 65 per cent of CaO in the forms of carbonate and hydrate. I t is dark gray or black in color, due t o t h e carbon present, a n d finds application as a n agricultural lime. The liquor removed from t h e filter is used in dissolving the next batch. H A K D L I K G T H E GAS
I n t h e manufacture of ammonium sulfate, as carried out extensively abroad, t h e mixture of steam and ammonia coming from t h e autoclave is led directly into a n absorber and produces a high-grade white sulfate. This production of sulfate is much simpler t h a n from ammonia liquor. Where t h e introduction of t h e accompanying steam is not permissible, as in the production of certain ammonia salts which cannot be subjected t o high temperatures, or where the process involves subsequent evaporation and crystallization, t h e ammonia-steam mixture coming from t h e autoclave is passed through a simple rectifying column provided with dephlegmator and condenser, a n d there is obtained therefrom a practically chemically
159
minute traces of a n unknown organic compound, b u t he has inferred t h a t the character and quantity of this impurity, from t h e manipulation of this apparatus, is largely mythical. For t h e production of nitric acid from ammonia, t h e product a s taken from t h e condensers attached t o t h e ammonia column is so pure t h a t no trouble is occasioned b y the poisoning of the catalyzers used in its subsequent oxidation. COMPLETE PLANT
I have with me assembled drawings of a n autoclave plant of 16 autoclaves, such as supplied t h e BirkelandEyde Co., which is similar to those intended for this country. T h e rated capacity of t h e plant is 75,000 lbs. of ammonia gas per day. Owing t o the present inability t o obtain this apparatus from Germany, where it has been manufactured on a n extensive scale, the American Cyanamid Company has redesigned t h e whole equipment, adapting it t o American standards and manufacturing conditions, and is now building this equipment in t h e Cnited States. E F F I C I E N C Y O F DECOMPOSITION
An extended study made b y the writer a year ago of one of the European plants which had been in operation for a long time, showed t h a t t h e transformation efficiency of the nitrogen in the Lime Nitrogen into ammonia was over 99 per cent. Our American plant is showing operating efficiencies, covering a period of several months, substantially equal t o the above. AUTOCLAVE P L A K T
An economical autoclave unit is one of eight working
Hr3. 0
/
2
3
4
5
6
FIG 3
pure ammonia gas. saturated with moisture a t t h e temperature of the condensing water. This rectifying column is self-acting because of t h e large quantity of steam admitted with the ammonia-steam mixture, and requires no attention whatever in its operation, other t h a n t o shut off the cooling water t o t h e condenser when not in use. The ammonia derived from the column, as before mentioned, is practically chemically pure, and is used directly in a large number of chemical industries. T h e Birkeland-Eyde engineers absorb this ammonia gas in distilled water, forming a dilute aqua ammonia, which t h e y add directly t o their dilute nitric acid for the manufacture of ammonium nitrate, t h e product being of extraordinary quality. On t h e other hand, ammonium nitrate of equal grade may be produced directly from t h e ammonia gases dehydrated in t h e column without t h e water absorption step. One of t h e large autoclave plants in France has been manufacturing anhydrous ammonia for years, a n d in addition t o the above purification system they have installed a n oil washer, charcoal filter and lime drying boxes before liquefaction. T h e oil washer, t h e writer was informed, was installed t o remove some very
shells. As t h e operating load factor on these autoclaves is very close t o I O O per cent i t is not necessary t o supply more t h a n one spare shell t o this eightautoclave equipment t o insure a full I O O per cent load factor. Such a plant of eight autoclaves would require a 300 h. p. boiler. I t was t h e old practice abroad t o set t h e safety valve on the autoclave shells a t 2 0 atmospheres and operate t h e boiler a t this same pressure. I n our own designs here in t h e States we have successfully operated a t I 2 j lbs. steam pressure without trouble and can t a k e steam from a common plant main. Superheated steam is preferable for t h e purpose, but not absolutely necessary. There is in addition required for operating the Lime Nitrogen feeding device, the stirrers in t h e autoclaves, t h e vacuum pump and the air compressor, and miscellaneous sludge disposal equipment, a continuous motor load of approximately I O O h. p. (the connected motor load would probably average about 2 0 0 h . p. depending upon local conditions). O P E R A T I N G COSTS
I n t h e compilation of a cost sheet for the production of ammonia from Lime Nitrogen there is such great
latitude in unit costs concerned t h a t the writer is presenting rather full quantitative d a t a t o which he is appending assumed unit costs. I n most cases the assumed unit costs are averages existing before t h e outbreak of the European war; t o these a n approximate return may be expected after its close. I n
I 60
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
a n y case t h e y may be readily corrected t o meet local conditions. LIDlE XITROGEN (26 PER CEXT AMYONIA) is unquestionably the cheapest source of nitrogen (ammonia) in this country. The sales prices are dependent to an extent upon the quantities and deliveries contracted for. The freight is allowed at $3.00 per ton of Lime Nitrogen shipped in special containers, which should cover the greater portion of territory in the United States lying within a 500 mile haulage radius of Niagara. CAUSTIC LIME is to be air-slaked on spot, z per cent weight of Lime Nitrogen used assumed at $6.00 per ton delivered. SODA ASH: 3.5 per cent of weight of Lime Nitrogen at $16.00 per ton delivered. POWER: IOO h. p. continuous at IC. per h. p. hour. STEAM at 30c. per 1000 lbs., 60 per cent weight Lime Nitrogen. WATER:z U. s. gals. per lb. ammonia. As the larger part of this is used in condensers and coolers the greater proportion may be salt water. Assumed at zc. per Ioao gals. LABOR AND SUPERINTENDENCE: Assumed at 300 men-hours per day at 30c. per man-hour. REPAIRS AND RENEWALS: $1.50 per ton ammonia, a record of long time operations. INTEREST: Assumed at 6 per cent on plant cost of $IZO,OOO. DEPRECIATION: On plant cost of $IZO,OOO depreciated in IO years, say 8 per cent. OPERATING COST
OF
AMMONIA PLANT
Capacity 30,000 Lbs. Ammonia per Day Gas Saturated with Water a t Cooling Water Temperatures PER LB. ITEM QUANTITY RATE PERDAY AMMONIA ..... $ 3.00 $180.00 Freight. . . . . . . . . . . . . . . . 7.20 6.00 Lime . . . . . . . . . . . . . . . . . . 1 . 2 0 tons 33.60 16.00 Soda.. . . . . . . . . . . . . . . . . . 2 . 1 0 tons 0.01 24.00 P o w e r . . . . . . . . . . . . . . . . . 2400 h. p. hr. 21.60 0.30 S t e a m . . . . . . . . . . . . . . . . . 7 2 M lbs. 1.20 0.02 W a t e r . . . . . . . . . . . . . . . . . 60 M gals. 90.00 0.30 Labor. . . . . . . . . . . . . . . . . . 300 men-hrs. ..... 22.50 Repairs and Renewals, . 20.00 ..... Interest. . . . . . . . . . . . . . . . .. 26,66 Depreciation. . . . . . . . . . . . .. 24.67 .. Miscellaneous. . . . . . . . . .
.
..
TOTAL CONVERSION COST (excluding NHI losses) $451.43 $0.01505 COST O F P L A N T
On account of t h e varied building conditions existing throughout t h e country i t is almost impossible t o give a detailed estimate of the cost of plant. A recent projection of such costs made b y this Company for a plant of this size, from which I have deducted t h e cost of land, foundations a n d sludge disposal, shows t h a t an ammonia plant of t h e size herein described could b e erected for about $IZO,OOO.This plant is designed t o produce as its final product a n ammonia gas cooled t o t h e temperature of t h e available water of t h e condensers, a n d , therefore, not strictly anhydrous. This figure further assumes t h a t water a n d power are furnished t h e plant, a n d no provision is made for power or pumping plants. Steel buildings with corrugated iron sides a n d roof, a n d of a type which h a r e demonstrated themselves a s fairly satisfactory for this service are included. The limitations imposed by building laws a n d choice of architecture may force one t o materially modify this estimate, as cheaper forms of construction may be used. On t h e other hand. many may prefer a more elaborate type of building t h a n provided in t h e above estimate, which would materially raise this figure.
Voi. 8,No. z
SUNMARY
The large number of installations operating with perfect success in various parts of t h e world for a number of years have demonstrated t h e commercial possibility of making ammonia from Lime Nitrogen. The plant in its present highly developed s t a t e is extremely certain in its action a n d simple t o operate. The efficiency obtained in t h e transformation of t h e nitrogen in Lime Nitrogen into ammonia gas is upwards of 98 per cent, or almost quantitative. T h e consumption of reagents is remarkably small, a n d t h e y are cheap a n d easy to obtain in almost all parts of t h e world. T h e quality of t h e ammonia produced b y this process is not surpassed b y a n y in t h e United States. It is chemically pure as produced a n d requires no further costly a n d tedious purification t o render i t available for t h e highest grade chemical products, or for t h e production of liquefied anhydrous product. The actual cost of production of this high-grade pure ammonia on a considerable scale, which enables o n e t o t a k e advantage of t h e lower prices at which Lime Nitrogen is offered, brings high-grade cyanamidammonia into t h e market almost as cheaply as t h e more impure forms already found there, a n d very much cheaper t h a n i t is possible t o obtain a n equal quality of ammonia from gas house liquor, t h e coke ovens, etc. N E W YORK CITY
MANGANESE IN GROUND WATER AND ITS REMOVAL B y S. B. APPLEBAUM Received June 10, 1915
Ground water as a source of municipal supply is constantly growing in importance. For many municipalities it is the only available source. For others, i t is often t h e best alternative when a surface supply, formerly wholesome a n d potable, becomes sewagepolluted. In this respect, well waters rarely fail t o meet t h e demands of modern sanitary science. It is only when engineering conditions of yield in d r y periods a n d chemical considerations of t h e mineral composition of such waters are taken up t h a t difficulties arise. T h e troubles resulting from t h e hardness or iron content of ground water a n d t h e most economical methods of removing these constituents are matters well understood. B u t t h e evil effects of manganese a n d t h e pressing need of i t s removal when i t is found present do not seem t o be fully appreciated b y our water works engineers. Superintendents of municipal water works rarely, if ever, have their supplies tested for manganese a n d t h e ordinary effects of t h a t element are often probably reported as iron troubles difficult t o cure. This article is a summary of t h e experience with manganese-containing waters of European cities, especially in t h e North German alluvial plains during t h e last decade. Further details a n d much valuable matter can be found in German publications b y R. Gans, H. Luhrig a n d Weiss, extracts of which have been printed in t h e Gesundheits-Ingenieur, Journal
