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u p according t o t h e formula a b o v e , 30 cc. should be sufficient. After t h e addition of t h e glyoxime, t h e solution is m a d e slightly alkaline with a m m o n i a , boiled for t w o m i n u t e s a n d t h e n set aside t o digest for one-half hour. T h e precipitate is c a u g h t on a t a r e d Gooch crucible, washed with zoo cc. of h o t water, dried for 45 minutes a t 120' C. a n d weighed. T h e weighed precipitate contains 20.31 per cent nickel. Prom t h e e q u a t i o n s given above t h e h y d r o c y a n i c acid or t h e potassium cyanide t i t r e of t h e solution can readily be calculated. If a chemically pure potassium c y a n i d e is a t h a n d , t h e a b o v e titres can be d e t e r m i n e d directly b y t i t r a t i n g weighed portions as directed i n t h e M e t h o d of Analysis'' given below. ( (
I f E T H O D O P ANALYSIS B O R ALKALI C Y A S I D E S
Five grams of the sample are dissolved in water a n d diluted t o exactly joo CC. Pipetted 50 cc. portions of t h i s solution are diluted with a n equal rrolume of water, t r e a t e d with I cc. of a m m o n i u n l hydroxide a n d 0 .5 cc. of t h e d i m e t h y l glyoxime solution a n d t h e n t i t r a t e d w i t h t h e s t a n d a r d nickel solution until a perm a n e n t red precipitate is produced. T h e color p l a y t o w a r d t h e e n d of t h e reaction resembles t h e m e t h y l o r a n g e e n d point observed i n t i t r a t i n g a n alkaline solution with a n acid solution. T h e nickel a m m o n i u m sulfate solution m a y be a d d e d rapidly a t first, p r o v i d e d t h e cyanide solution is vigorously s t i r r e d ; t o w a r d t h e end point t h e addition should be slower a n d t h e stirring more rapid. If more t h a n 0 .5 cc. of glyoxime is used, t h e e n d point shows a t e n d e n c y t o a p p e a r too soon unless t h e addition of t h e s t a n d a r d solution is slow a n d t h e agitation of t h e solution very brisk. T h e cyanide dilution m a y ' be varied w i t h o u t serious e f f e c t ; however, t h e m e t h o d works better when t h e volume is approximately IOo cc. A large of a m m o n i u m hydroxide delays t h e e n d p o i n t ; I t o j cc. i n t h e volume specified does n o h a r m . A titration requiring 5 0 cc. of t h e s t a n d a r d solution costs onefifth of a cent. I n t i t r a t i n g solutions which contain hydrocyanic acid, a measured volume of solution is m a d e alkaline with ammonium hydroxide and then treated as above. Table I shows the values obtained on different cyanide samples by the new method and by two of t h e older methods. TABLEI-ANALYSES
DIFFERENTMETHODS-PERCENTAGES HCN Gravimetric New Liebig's method(a) method method 39.35 39.16 39.55 39.25 39.00 39.57 40.71 40.79 . . . . . . . . . . . 40.75 . , , , , . . _ ., . 33.58 33.55 33.70 . . . . . . . . . . 0.59 0.595 0.60 , . 0.050 0.050 0.051 7 Oil of bitter almond water.. , , , 0.076 0.076 0.077 (a) Corrected for chlorides. BY
Sample 1 KCN . . . . . . . . . . . . . . . . . 2 KCN. . . . . . . . . . . . . . . . .
Vol. 6, No. 7
T a b l e I1 d e m o n s t r a t e s t h e accuracy of t h e new m e t h o d in t h e presence of possible impurities in commercial cyanide samples : TABLE11-TITRATIONSOF MIXTURES 50 cc. of 1 per cent KCPU' solution used in each titration Cc. nickel Cc. nickel ammonium Perammonium Persulfate centage Reagent sulfate centage required error added required error x o n e . . . . . . . . . . . . 49.45 0.00 1 g. xaC1 . . . . . . . . 49.47 + 0 . 0 4 1 g. K C N O . . ..... 49.45 0.00 1 g. "4NOa.. . . . 49.39 -0.12 1 g. K C N S ....... 4 9 . 4 6 i-0.02 1 g . NaHCOa.. 49.42 - 0 . 0 6 ;ggg,K&?& 4 9 . 4 1 -0.08 0.1 g. KOH 49.5 0.00 4 9 , 5 5 +o,20 g, K O H , , 20 g. KzCOa.. 49.62 +0.34 0 . 3 g. C a N C N . . . 4 9 . 4 6 + O . O Z 1 g. KZSO4.. . . . . . . 4 9 . 4 3 - 0 . 0 4 0.1 g. KaFe(CN)a. 4 9 . 4 8 + 0 . 0 6 I g. N H ~ C ~ . 49.42 -0.06 1 g. K4Fe(CN)n.. 50 75 f 2 . 6 3
"a,",;'
..
....
This table demonstrates the remarkable freedom of t h e m e t h o d f r o m interfering substances. KOH a n d KaFe(C1C')Ginterfere when present in large a m o u n t s ; t h e small quantities usually present in commercial 'yanides have.'practically no effect at T a b l e 111 shows t h e accuracy of t h e m e t h o d in t h e presence Of the double cyanides used i n electroplating* TABLE 111-TITRATIOSS Double cyanide present K A g ( C N ) z . ,. . . . . . . . . . . KCu(CN)g.. . . . ,. KzZn(CN)4.. ..
...
IN
PRESENCEOF DOUBLECYANIDES G. K C N Percentage found error 0,1205 - 0.25 0.1906 0.47 0.4612 4-31.02
G. K C N added 0.1208 0,1915 0.3520
.
-
It is Seen that the method gives only the cyanide in silver a n d copper c y a n i d e solutions. Experiments show that than the free cyanide is o b t a i n e d in zinc cyanide solutions, the end point occurring when the Zn : KcN ratio is approximately I : o.6, In copper and silver cyanide solutions Liebigls method works the Same as the new method. In zinc cyanide solutions Liebig's method gives the total cyanide, t h a t is, t h e free c y a n i d e plus t h e cyanogen in the zinc' d o u b l e cyanide. Hannay,s method gives t h e t o t a l cyanide in all t h r e e cases. This is a d i s a d v a n t a g e because only t h e free cyanide is ordinarily desired. S U IfMARY
T h e new m e t h o d for t h e d e t e r m i n a t i o n of h y d r o cyanic acid a n d t h e alkali cyanides consists in m a k i n g t h e cyanide solution ammoniacal, t h e n a d d i n g a small a m o u n t of methyl glyoxime solution a n d finally t i t r a ting t h i s prepared solution w i t h a s t a n d a r d nickel a m m o n i u m sulfate solution until a p e r m a n e n t red precipitate is produced. T h e preceding pages show t h a t t h e new m e t h o d is accurate, free f r o m o r d i n a r y interferences, usable in cloudy solutions, rapid, c h e a p a n d of value in titrations of double cyanides. DEPARTMENT OF CHEMISTRY, CORNELL UNIVERSITY ITHACA, NEW YORK
.
T h e results o b t a i n e d b y all three m e t h o d s check ' closely on Samples 3, 4, 5 , 6 a n d 7 . T h e values on Samples I a n d z are n o t i n such good agreement b u t it is seen t h a t t h e new m e t h o d checks u p t h e corrected gravimetric m e t h o d better t h a n does Liebig's m e t h o d . Qualitative tests showed small a m o u n t s of sulfoc y a n a t e s a n d ferrocyanides, b o t h of which would cause high results in t h e gravimetric m e t h o d a n d Liebig's m e t h o d .
A METHOD FOR THE RAPID QUANTITATIVE ANALYSIS OF BRONZE AND BRASS' (Pb, Cu, Sn, Sb, Fe and Zn) B y RICHARD EDWINLEE, JOHNP.
"RICKEY
AND
WALTERH. FEGELY
I N T R? D U C TI 0 N
T h e method of analysis reported in t h i s p a p e r is t h e o u t g r o w t h of a n investigation t h a t was u n d e r t a k e n as t h e result of a request m a d e t o one of us sometime 1 Presented at the 49th meeting of the American Chemical Society. Cincinnati, April 6-10, 1914.
J u l y , 1914
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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
ago t o t a k e charge of some “control” work for a large c o m p a n y manufacturing bronze metal i n various forms. Most of t h e metal is sold on specification. T h e alloy supplied b y t h i s firm varies i n composition as follows: C u , 6 j t o 69 per c e n t ; P b , a j t o 30 per c e n t ; S n , 5 t o 6 per c e n t ; F e , 0.1t o 0.3 per c e n t ; Zn, 1.5 t o 3 per cent. T h e requirements were t h a t t h e analysis be accurate t o 0.2 per cent a n d t h a t t h e t i m e consumed in making t h e complete analysis should n o t exceed one hour, preferably 4 j minutes. On receipt of this request t h e a u t h o r s began immediately t o m a k e a careful survey of t h e literature relating t o t h e analysis of bronze a n d brass i n t h e hope t h a t i t would be possible t o find a method a d a p t e d t o their needs. Over t w o m o n t h s were devoted t o testing t h e various proposed methods with ‘known mixtures’ of t h e metals comprising t h e alloy. T h e a u t h o r s hesitate t o s a y whether t h e fault l a y with themselves or was inherent in t h e methods, b u t most discouraging results were obtained although each m e t h o d was tested repeatedly with t h e exercise of much care. We were finally confronted with t h e following perplexing situat i o n : on t h e one h a n d , such methods a s were f o u n d t o give t h e required accuracy were t o o long a n d tedious; o n t h e other h a n d , t h e few methods proposed for rapid analyses failed in our h a n d s t o give n o t only t h e desired accuracy, b u t t h e accuracy claimed for t h e methods by their respective authors. T h i s experimental survey, however, was n o t without value, a s i t rendered possible n o t only t h e detection of inaccuracies i n m a n y of t h e recommended procedures, b u t t h e selection of t h e best processes involved i n such of t h e proposed methods as most closely approximated bur w a n t s F u r t h e r m o r e , i t facilitated t h e formulation of conditicns best a d a p t e d t o securing t h e desired e n d . E a r l y in t h e investigation i t became obvious t h a t i t would contribute greatly t o t h e rapidity of t h e determinations if a method could be formulated which would provide for t h e using of a separate portion of t h e alloy for each determination. T h e more accurate of t h e proposed methods are as a rule, open t o t h e serious objection t h a t one portion of t h e alloy is used for several determinations. Such procedure. however, is time-consuming. I n t h e method of analysis proposed i n t h i s p a p e r all t h e metals are determined i n separate portions of t h e alloy with t h e exception of zinc which is determined i n t h e filtrate f r o m t h e iron if t h e l a t t e r is present. W h e n t h e iron is a b s e n t from t h e sample t h e zinc is determined i n a separate portion in a b o u t t h i r t y minutes. T h e a u t h o r s make n o particular claim t o originality for t h e scheme of znalysis s u b m i t t e d herewith as most of t h e methods are based upon reactions familiar t o all chemists. F u r t h e r m o r e , some of t h e m h a v e been employed b y Low, Demorest, P. H. Walker a n d T h i t m a n a n d other well known contributors t o industrial analysis as a basis of s t a n d a r d methods for single determinations. However, t h e modifications of t h e selected procedures a n d their application t o t h e complete analysis of bronzes of t h e s t a t e d composition, t h e s t u d y of t h e sources of error a n d t h e conditions most favorable for procuring t h e desired results b y means of t h e
557
a d o p t e d procedures together with t h e formulation of such new processes a s were necessary t o articulate t h e different procedures, are some of t h e problems- which h a v e been a t t a c k e d . T h e accuracy of t h e methods is shown b y t h e experimental results recorded i n P a r t 11, T e s t Esperiments. As a f u r t h e r confirmation of t h e dependability of t h e method it m a y be noted t h a t t h e procedure described herein h a s been used with equally good results n o t only b y t h e s t u d e n t s in this laboratory b u t also b y t h e chemists in one large testing laboratory’ for a period of nearly t h r e e months. P A R T I-METHOD
OF AXALYSIS
D E T E R M I X A T I O N O F LEAD
PROCEDURE-TO 0 . 5 g r a m of t h e alloy in a 300 cc.
*
Erlenmeyer flask, a d d 1 2 cc. of water containing 4 g r a m s of t a r t a r i c acid, a n d t h e n 4 cc. of conc. H N 0 3 . Place o n a h o t plate t o dissolve t h e alloy quickly. ( T h e solution should be perfectly clear; if n o t , reject i t a n d repeat t h e procedure.) Remove t h e solution from t h e h o t plate, allow t o cool for I t o z minutes, a d d I O cc. conc. H2S01, a n d t h e n heat on h o t plate until all (Caution: Care m u s t nitrous fumes are expelled. be exercised n o t t o carry t h e procedure beyond t h i s stage or t h e t a r t a r i c acid will be decomposed.) Dilute with I O O cc. of cold water, a d d 7 j cc. of e t h y l alcohol, shake, allow t o s t a n d for z or 3 minutes, filter through a weighed gooch crucible, wash with water t o which a little H2S04 has been added, until t h e precipitate is white a n d t h e n wash o u t acid with alcohol. Reject t h e filtrate. D r y t h e precipitate in crucible on h o t plate, a n d t h e n h e a t t o dull redness with t h e Bunsen burner for a fern minutes. Cool a n d weigh as PbSO,. W t . PbSt), X 0.683*= wt. P b order to prevent occlusion and adsorption of the Cu salts by the lead sulfate precipitate, it was found necessary t o make the solution from which the lead precipitate is separated by filtration, relatively large. The solution of the lead sulfate is prevented by the addition of alcohol. a-In case the alloy contains a small percentage of lead, it is advisable, of course, to use a relatively large amount of the sample. If this is done. the quantities of the reagents employed, including water and alcohol, should be increased proportionately. The reasons for this procedure are obvious. In the first place, unless the volume of the solution is made larger the concentration of the Cu and other metals present becomes very large owing t o the use of larger amounts of sample. This will increase the error due t o occlusion and adsorption as mentioned in Note I . In the second place, in order to preserve the proper concentration of sulfate ions for the complete precipitation of Pb in this larger volume of solution it is necessary t o use larger amounts of the reagent, sulfuric acid. NOTES-I-In
DETERMINATIOK O F COPPER
PRocEDcm-Place 0 . j g r a m of t h e alloy in a 4 0 0 cc. beaker, a d d j t o I O cc. of dilute HNOs (I-I), cover beaker mith a watch glass until violent action ceases, t h e n remove watch glass a n d evaporate o n h o t plate t o s y r u p y consistency. Dilute t o a b o u t zoo cc. a n d a d d K O H solution until a small precipitate of copper hydroxide persists after thorough stirring. Now a d d acetic acid until t h e copper precipitate is completely 1
The Meadville Testing Laboratory, Meadville.
5 58
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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
T‘ol. 6 , KO. 7
dissolved, t h e n a d d a small excess of the acid. Cool wash, a n d t h e n with h o t water. P o u r t h e filtrate i n t o t h e mixture t o t a p - w a t e r t e m p e r a t u r e , t h e n a d d 40 a joo cc. beaker a n d reserve for check determination cc. of t h e K I solution (100g r a m s t o I 1.) a n d j cc. of of copper. D r y t h e crucible a n d contents on h o t p l a t e s t a r c h solution, a n d t i t r a t e immediately with s t a n d a r d and t h e n ignite at red h e a t f o r t e n minutes. T h e igNa2Sz03 solution until t h e blue color disappears. nited residue consists of SnOz and a n y S b (as Sb204) NoTEs-I-It has been pointed out by Walker and Whitman‘ which m a y h a v e been present i n t h e alloy. that the results obtained by following Low’s iodide method2 Wt. SnOz ( a n d Sb104) X 0.788 = wt. Sn ( a n d Sb) are uniformly a little low. They add “this error is not due to NOTES-1-The results obtained by this method are usually the method which gives exceedingly accurate results, but to the a little high, owing to the fact that the precipitate frequently fact that nearly 6 per cent of the copper is not precipitated as contains traces of the oxides of Cu, Sb, and Pb. However, the cuprous oxide. This loss is uniform for if we add 6 per cent of digestion of the dried residue in dilute nitric acid and the final the copper determined, the result will be the per cent of the copseparation of the preclpitate from a large volume of solution, per in the alloys.” This is undoubtedly true. Their further tend to reduce errors from this source. The precipitate will also statements, however, that when an alloy containing 5 per cent contain any phosphorus that is present in the sample. of copper is decomposed by nitric acid, evaporated to dryness, n-Much time and energy were consumed in an effort to obtain taken up with nitric acid and filtered, the error in determining a volumetric method for determining tin in a separate portion the copper in the filtrate will frequently be o 5 to 0.7 per cent, of the alloy. One of the most attractive volumetric methods for cannot be confirmed by our experience. By following the promaking this determination is Walker and Whitman’s modificaposed method of standardization and analysis, which is essentially tion‘ of Low’s iodimetric method. Our efforts, however, to Low’s method we have been able to check within 0.1per cent adapt it to our scheme of analysis were without success. The repeatedly. chief obstacle to its application to the rapid analysis of bronze n-Provision has not been made in the method as formulated is the presence of relatively large percentage of Cu in the alloy. for the separation of copper from any other metals, yet care The method, however, was found to give excellent results when must be exercised to exclude from the solution prepared for titraused in making analyses of Babbitt metal if the percentage of tion any substances which will either liberate or absorb iodine Cu in the alloy was small; but if the percentage of Cu was large Therefore, free C1, free Br, nitrous oxides, ferric ions, and As the results came high, owing to the fact that during the reduction and Sb in the ‘ous’ condition must be absent. of the Sn the Cu was reduced to cuprous chloride which takes up Ferric ions may be removed by adding ammonium fluoride, a portion of the iodine when the solution is finally titrated. Our which interacts with the former to produce ferric fluoride. This results in regard to the errors introduced by the titration of Sn latter substance which is only slightly ionized has little or no in the presence of Cu agree with those obtained by Ibbotson and oxidizing power and, therefore, cannot liberate iodine under the Aitchison.2 existing conditions. (CHECKD E T E R M I N A T I O N O F C O P P E R ) The trivalent arsenic and antimony, if present, must be oxidized PROCEDURE-Coo1 t h e filtrate f r o m t h e Sn deExcess to the pentavalent condition by the addition of bromine. of bromine must be removed by boiling the solution before termination, a d d &OH solution until a small precipitate of copper hydroxide persists after thorough titrating. No other elements intqrfere with the procedure. stirring. A d d acetic acid until t h e copper precipitate 3-Pb, Bi, and Cd, if present, interact with the K I and form is completely dissolved, t h e n a d d a . small excess of the corresponding yellow insoluble iodides. This causes no t h e acid. Follow directions as given u n d e r Determinatrouble, however, in fact many chemists regard the presence of tion of Copper. one or more of these metals as a distinct advantage as the presDETERUIKATION O F AiYTIMOSY ence of the yellow precipitate assists the operator in securing uniform end points. In this laboratory it is customary to add PROCEDURE-iveigh o u t 0 . j g r a m of t h e fine drillings a few cc. of a solution of lead acetate to the solution to be titrated of t h e alloy i n t o a 300 cc. Kjeldahl flask, a d d z j CC. if it is known that Pb is not present. of conc. sulfuric acid a n d h e a t over t h e b a r e flame of a 4-In order that the liberated iodine may be held in solution Bunsen burner. K e e p t h e acid a t i t s boiling point i t is necessary to use rather large excess of KI. This procedure until t h e solution is clear or t h e residue is white. Cool, increases the speed of the reaction. a d d I O O cc. of water, boil for several minutes and t r a n s 5-The presence of an excess of inorganic acid interferes with the procedure. It should be remembered, however, that fer t h e contents of t h e flask t o a 400 cc. beaker. Dilute unless the solution contains a sufficient excess of acetic acid the t o zoo cc., h e a t t o 7 0 ° C. (158’ F.) a n d t i t r a t e with a s t a n d a r d KMnOk solution. T h e p e r m a n g a n a t e soluend point will not be sharp. 6-The solution should always be cooled to tap water tem- t i o n should b e a d d e d rapidly until t h e p e r m a n g a n a t e perature just before the K I solution is added. color persists, t h e n a d d several cc. in excess. S t i r 7-It should be remembered that the Sn present will make an t h e solution vigorously, a n d t h e n t i t r a t e with a s t a n d insoluble residue in the solution prepared for titration. a r d solution of ferrous a m m o n i u m sulfate until t h e pink color j u s t disappears. D E T E R M I N A T I O N O F TIN ( A N DSb) NOTES--I-Although antimony is not found in the majority PROCEDURE-weigh 0.5 g . Of t h e alloy i n t o a 400 CC. of bronzes and brasses i t frequently occurs alloyed with variable beaker, a d d 5 t o I O cc. of dil. “ 0 3 (I-I), cover with percentages of lead, tin, copper and iron. Therefore, in order to a w a t c h glass until violent action ceases, t h e n remove make the present scheme of analysis as wide as possible in its c o v e r a n d e v a p o r a t e t o a p a s t e o n h o t plate. A d d application and thereby increase its usefulness, it was deemed 1 5 cc. of dil. ” 0 3 , boil for several minutes a n d dilute advisable to incorporate a method for the rapid determination t o a b o u t 2 0 0 cc. Boil for a few minutes, filter t h r o u g h of Sb. z-The method is a t once recognized as a modification of a weighed Gooch crucible, wash with h o t nitric acid 1
THISJOURNAL, 1
f
Jour. Am. Chcm SOC.,24 (1902), 1082
(1909), 519.
1
2
THISJOURNAL, 1 (19091, 519. Chem A‘ews, 107 (1913). 109, also C . A , , 7 (1913), 2025, 8 (19141, 476.
J u l y , 1911
T H E J O C R N A L O F I - V D l - S T R I A L A,VD E N G I N E E R I N G C H E M I S T R Y
Low's well known method.' The chief difficulty we experienced in fitting i t to our scheme of analysis was the matter of securing Sb in a suitable condition in sulfuric acid solution. Alloys containing a high percentage of copper resist solution by the usual procedure. Nitric acid is eliminated as a solvent because of its oxidizing action; and HC1and KClOaare ineff ectiveunless the treatment is greatly prolonged. Finally, the not-entirely satisfactory method of decomposing the alloy in conc. sulfuric acid in a Kjeldahl flask exposed to the bare flame of a Bunsen burner was adopted. Complete decomposition is usually effected in ten to twenty minutes, after which the determination may be readily finished in IO minutes. After one or two trials, it will probably be found that the blue color imparted to the solution by the presence of the copper does not hinder the determination of the exact end point when the permanganate is added. 3-Demorest has pointed out in an excellent paper2 that it is necessary to employ a large excess of potassium permanganate to complete the oxidation of the Sb. I t is not best to have HC1 present when the antimony is titrated as the end point is made very transient by its presence. D E T E R M I S A T I O K O F I R O l - .ASD Z I S C
PROCEDURE-TO 0.j g r a m of t h e alloy i n a 400 cc. (1-1) t o dissolve beaker a d d sufficient dilute "03 t h e sample. H e a t o n h o t p l a t e u a t i l t h e alloy is thoroughly decomposed, t h e n e v a p o r a t e t h e solution just t o dryness. .idd I O cc. of conc. HC1 a n d I O O cc. of w a t e r , h e a t t o a b o u t 70' C . a n d pass H2S t h r o u g h t h e m i x t u r e until all t h e P b , Cu, Sn? a n d S b ( C d , e t c . ) a r e precipitated. F i l t e r , using a B u c h n e r funnel with an asbestos m a t , wash t h e precipitate w i t h m-ater. T h e filtrate which contains t h e iron and zinc should be transferred t o a j o o cc. beaker. NOTE-A drop of this filtrate should be transferred to a spot plate and tested with a drop of potassium ferrocyanide for the presence of Cu and Fe which are interfering substances and if present in weighable quantities they should be removed. If Cu is present which will be indicated by the presence of red coloration, treat the filtrate again with hydrogen sulfide and filter; if Fe is present which will be indicated by the appearance of a blue coloration, proceed as directed under ( z ) , Iron and Zinc. I-ZISC, I F F E I S ABsEIiT-Dilute t h e filtrate t o 2 0 0 cc.. h e a t t o 70' C. a n d t i t r a t e w i t h s t a n d a r d potass i u m ferrocyanide, using ferric chloride or u r a n y l n i t r a t e as an indicator. T h e t i t r a t i o n should b e perf o r m e d slowly 2 n d w i t h c o n s t a n t stirring i n order t o o b t a i n t h e most satisfactory results. C o n t i n u e t o a d d t h e ferrocyanide until a d r o p of t h e solution i n t h e b e a k e r shows a bluish green t i n g e (brown tinge when u r a n y l n i t r a t e is used as an indicator) when t e s t e d o n a white porcelain p l a t e with 2 d r o p of ferric chloride after s t a n d i n g a few seconds. T h e q u a n t i t y of t h e s t a n d a r d solution which is required t o produce a good e n d point i n t h e b l a n k determination m a d e a t t h e t i m e of standardizing t h e solution, m u s t b e s u b t r a c t e d f r o m t h e a m o u n t of s t a n d a r d used i n m a k i n g t h e determination. h-OTE-I-cOf'?'eCtiO% for Blank. As the indicators are not very sensitive under the imposed conditions it is necessary to determine the excess of standard solution required to effect the color change of the indicator used. A 'blank' must be run, therefore, using the same quantities of reagents under corresponding conditions of volume, temperature and acidity. 1
THISJ O U R N A L , 5 (1913), 842. I b i d , 5 (1913), 842
559
2-If the solution turns blue during the titration, it is an indication of the presence of small quantities of iron. 2-IRO?; ASD zIzrc-Add 2 cc. of concentrated " 0 3 t o t h e filtrate t o oxidize t h e F e , h e a t t o boiling, a d d 2 j CC. of j N NHdCl a n d t h e n ",OH until t h e odor of t h e reagent barely persists after boiling t h e mixture for one minute. Filter off t h e Fe(OH)3 a n d ignite. Weigh as F e 2 0 s . NOTES-I-zinC is completely precipitated from " 2 1 solutions by potassium ferrocyanide as white zinc ferrocyanide Such metals as Pb, Cu, Sn, Fe and >In are also precipitated by this reagent, and therefore must be removed before the Zn is titrated. 2-The acid solution must not contain free C1, free Br or the oxides of chlorine as these substances decompose ferrocyanide. 3-Care must be taken to conduct the standardization as well as all determinations under corresponding conditions with particular reference to volume, temperature, acidity, amount of ammonium salts and the rate of titration. Furthermore, it is imperative that the titration be conducted slowly and with constant stirring of the solution. If this precaution is not observed the end point will be reached apparently before all the zinc is precipitated. P A R T 11-TEST
EXPERIMESTS
I n order t o m a k e a fin21 t e s t of t h e accuracy and general applicability of t h e procedures recommended i n t h i s p a p e r , five series of experiments-each series consisting of six s e p a r a t e determinations were m a d e . I n m a k i n g t h i s t e s t , t h e results of which a r e reported herewith, a s t a n d a r d bronze alloy was used unless t h e r e is a n o t e t o t h e contrary. E q u a l l y good results were obtained when k n o w n mixtures were employed. S E R I E S I-LEAD \Vt. of P b W t . of h-umber of sample present exoeriment Grams Gram 0.0467 (1) . . . . . . . . . . . . . . . . . 1.0055 0.0464 ( ? ) . . . . . . . . . . . . . . . . . 1.0005 0.0463 (3) . . . . . . . . . . . . . . . . . 0,9995 ( I ) . . . . . . . . . . . . . . . . . 0.2013 0.1562 (2) . . . . . . . . . . . . . . . . . 0.2114 0.1639 (3) . . . . . . . . . . . . . . . . . 0.2266 0.1757
W t . of P b Error found percentage Gram comoosition 0.0469 O0.0270 0.0465 O0.017,0 0.0464 O0,017G 0.1559 00.10% 0.1642 00.15% 0.1754 OO.lSc/,
A s t a n d a r d B a b b i t t metal w a s employed i n m a k i n g t h e l a s t t h r e e determinations reported i n t h e foregoing series. S E R I E S 11-COPPER W t . of Cu Wt. of Cu Error W t . of present found percentage sample Gram Gram composition Gram 0,3047 00 1oyo 0.5018 0.3042 0.3112 00 0 8 7 , 0.3116 (2) . . . . . . . . . . . . . . . . 0.5133 0.3160 00 10% 0.3160 (3) . . . . . . . . . . . . . . . . . 0.5212 0.3001 0 3009 00 187, (4) . . . . . . . . . . . . . . . . . 0 , 4 9 5 6 0.3107 0.3104 (5) . . . . . . . . . . . . . . . . . 0.5120 00 06% 00 OSc$ 0.3084 0.3088 (6) . . . . . . . . . . . . . . . . . 0.5094
Piumber of experiment (1) . . . . . . . . . . . . . . . . .
S E R I E S 111-TIS W t . of Wt. of Sn W t . of Sn found sample present Number of Gram Grams Gram experiment 0.0238 0.0242 1.0000 (1). . . . . . . . . . . 0,0251 1,0000 0.0238 (2). . . . . . . . . . . 0.0252 1,0000 0.0238 (.3,) . . . . . . . . . . . (1) . . . . . . . . . . . . . . . . . 0.5000 0.0119 0.0120 (2) . . . . . . . . . . . . . . . . . 0 , 5 0 0 0 0,0119 0,0123 0,0122 0.0119 (3). , . , , , . , . . , , . . , , , 0 , 5 0 0 0 S E R I E S I V-
Error percentage composition 00.047, 00. 137; 00.14% 00.02% 00.08% 00 069;
-A N T I bI 0 S Y
A s t a n d a r d B a b b i t t m e t a l , containing 77.53 per cent of Pb, 0 . j 8 per cent of Cu, 10.03 per cent of Sn, a n d I 1.6 j p e r cent of Sb, w a s employed i n making t h e t e s t s , t h e results of which are recorded i n t h e following series. In t h e first t w o determinations t h e Pb w a s removed a s P b S 0 4 before t i t r a t i n g with K1\In04; i n t h e following f o u r determinations t h e t i t r a t i o n was conducted i n t h e presence of t h e P b S 0 4 ; a n d i n t h e
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
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Vol. 6, KO. 7
v a l u a t i o n according t o t h e a m o u n t of fiber wood will yield, which is t h e chief concern of m a n u f a c t u r e r s of chemical pulps. Wt. of Wt. of S b W t . of S b Error present found percentage Number of sample T o m a k e effective a n y of these units a s a basis for Gram Gram composition experiment Gram evaluating wood for pulp we m u s t resort t o a n efficient (1) . . . . . . . . . . . . . . . . . 0.3000 0.0350 0.0349 O0.0370 ( 2 ) . . . . . . . . . . . . . . . . . 0.3000 0.0350 0.0349 O0.0370 s y s t e m of sampling which will be t r u l y representative. 0.0350 0.0349 U0.0370 (1) . . . . . . . . . . . . . . . . . 0.3000 0.0350 0.0359 ( Z ) . , . . . . . . . . . . . . . . . 0.3000 00.0370 Such a s y s t e m was described i n t h e author's f o r m e r 0.0353 (3) . . . . . . . . . . . . . . . . . 0,3027 0.0354 00.037, 0.9353 (4) ................. 0.3027 0.0356 00.09% paper. (1) . . . . . . . . . . . . . . . . . 0 0327 0.0353 0.0354 00.03% T h e need of such a basis for valuing wood is a t once ( Z ) , . . . . . . . . . . . . . . . . O:d327 0.0353 0.0354 00.03% a p p a r e n t when we s t o p t o t h i n k of t h e great variation T h e a b o v e results indicate t h a t t h e presence of t h e i n t h e quality of t h e s a m e species, depending upon P b a n d Cu salts d o n o t interfere with t h e t i t r a t i o n of i t s h a b i t a n d conditions of g r o w t h . P o p l a r s of our S b with KhinO4. n o r t h e r n s t a t e s differ greatly f r o m those of t h e middle S E R I E S V-ZINC s o u t h e r n s t a t e s . T h e m e a s u r e m e n t of value b y cord Wt. of W t . of Zn Wt. of Zn Error or solid c o n t e n t s t a k e s n o a c c o u n t of yield in pulp. sample present found percentage Number of Gram Gram Gram composition experiment Other species of similar external characteristics are (1) . . . . . . . . . . . . . . . . . 0.4985 0.1497 0.1492 O0.1070 often mixed in, as Bass wood w i t h poplar, a n d fir ( 2 ) . . . . . . . . . . . . . . . . . 0.4969 0.1492 0.1497 O0.1170 0.1494 0.1497 00.0670 ( 3 ) , . . . . . . . . . . . . . . . . 0.4975 a n d hemlock with spruce. Such mixtures i n late 0.1494 ( 4 ) . . . . . . . . . . . . . . . . . 0.4977 0.1495 O0.0Z70 0.1495 0.1496 ( S ) . . . . . . . . . . . . . . . . . 9.4979 00.029 years h a v e been p e r m i t t e d , when t h e characteristics ( 6 ) . . . . . . . . . . . . . . . . . 0.5004 0.1503 0.1505 00.048 a r e near enough t o cause n o trouble in cooking. Aside P A R T 111-SUMMARY f r o m these differences i n species, a n d h a b i t of g r o w t h , I-A s u r v e y of a large n u m b e r of proposed m e t h o d s t h e r e is t h e quality of t h e wood, as such, which should for t h e analysis of bronze a n d brass h a s been made.. be t a k e n i n t o account in i t s bearing on yield of pulp. T h e m a j o r i t y of t h e m e t h o d s h a v e been f o u n d t o be Wood is subject t o disease a n d decay a n d all such t o o long a n d elaborate; or if in t h e class of rapid m e t h - defective wood will n o t give t h e n o r m a l prqduct. ods, t o o inaccurate t o be suitable even for control W i t h a view t o discovering t h e influence of these work. various factors u p o n t h e yield, a large n u m b e r of de11-A m e t h o d h a s been proposed for t h e analysis t e r m i n a t i o n s of t h e cellulose were m a d e b y t h e Cross of bronze a n d brass containing P b , Cu, Sn, S b , Fe, a n d a n d B e v a n chlorination m e t h o d . Zn b y which t h e d e t e r m i n a t i o n s m a y be m a d e with PROCEDURE-The stick t o be tested was q u a r t e r greater rapidity t h a n a n y other m e t h o d s of analysis s a w n , a n d t h e sample was o b t a i n e d b y planing t h i n known t o t h e authors. Working with t h e usual lab- shavings f r o m t h e face of t h e q u a r t e r . I n this way o r a t o r y facilities i t h a s been f o u n d t h a t after t h e s a m - t h e s a m p l e would include a p a r t of t h e growth f r o m ples h a v e been weighed t h e d e t e r m i n a t i o n s of P b , t h e center t o t h e b a r k . We f o u n d such t h i n s h a ~ i n g s S n a n d S b i n t h r e e different alloys c a n be easily commuch more satisfactory t h a n a n y other form. T h r e e pleted i n one a n d one-half t o t w o hours. g r a m s of t h e shavings, previously dried a t 100' C . , 111-The d e t e r m i n a t i o n s m a d e b y t h i s m e t h o d n o t were boiled for a b o u t half a n h o u r in I per cent sodium only agreed a m o n g themselves b u t t h e y were more h y d r a t e . T h e mass was t h e n well washed a n d squeezed accurate t h a n those m a d e b y t h e longer m e t h o d s . a n d placed u n d e r a bell-glass, i n t o which was led T h e m a x i m u m error of a n y d e t e r m i n a t i o n i n a n y series a slow s t r e a m of chlorine gas. Complete conversion was 0.1j per cent. T h e average error, however, is of t h e lignone usually followed i n one hour's exposure much less. t o t h e gas. It was t h e n well washed t o remove h y d r o IV-The accuracy a n d general applicability of t h e chloric acid a n d impurities a n d placed in a t w o per cent proposed m e t h o d h a s been shown b y t h e series of t e s t solution of sodium sulfite containing 0.2 per cent experiments, a n d f u r t h e r confirmed b y t h e report of sodium h y d r a t e , a n d boiled for a b o u t five minutes. one commercial l a b o r a t o r y where t h e m e t h o d h a s been T h e fiber was t h e n well washed with h o t water a n d constantly employed for nearly t h r e e m o n t h s . t h i s t r e a t m e n t with sodium sulfite a n d h y d r a t e reCHEMICAL LABORATORY, ALLEGHENY COLLEGE p e a t e d if f o u n d necessary. T h e fiber was f o u n d MEADVILLE, PA. almost p u r e a n d nearly white.' It was t h e n dried, weighed a n d results calculated. T a b l e I gives t h e characteristics of 24 samples of THE CHEMICAL EVALUATION OF WOOD FOR PULP' B y M . L. GRIFFIN mixed spruce a n d brilsam fir f r o m M o n t m o r e n c y in I n a previous paper,* t h e a u t h o r showed t h e inade- C a n a d a . T h e samples were selected t o show t h e q u a c y of t h e cord 'measure a s a unit for valuing pulp various factors influencing t h e yield in chemical fiber. wood, resulting in great variation in t h e solid volume, E i g h t of these samples were chosen f r o m wood of recogd u e t o various factors. As a b e t t e r s t a n d a r d he nized good quality for comparison. F r o m a review a d v o c a t e d a solid unit, t h e cubic foot, a n d illustrated of t h e table a n d t h e samples we observe: I-That density of a n n u a l ring g r o w t h is n o t neceshow such a unit could be a d a p t e d i n practice w i t h o u t inconvenience. A unit of weight a s a still more re- sarily proportional t o specific g r a v i t y (see N o s . I , liable basis was also a d v o c a t e d . T h e r e remains t h e 7, 9, 23 a n d 24) a n d t h a t specific g r a v i t y is n o t prol a s t t w o d e t e r m i n a t i o n s t h e t i t r a t i o n was m a d e i n t h e presence of b o t h P b a n d C u salts.
1
1914.
Presented before the Maine Section of t h e A. C. S.. Auburn, M a y 1,
* See abstract,
THIS.JOURNAL, 6, 163.
1 T o remove t h e last residues of non-cellulosic matter, it may be bleached with hypochlorite or permanganate. I f with the latter, i t will be necessary t o wash with a weak solution of sulfurous gas.
