I S D U S T R I A L A S D E S G I S E E R I S G CHEXIISTRY
January 15, 1930
constitution and in the determination of the purity of compounds whose constitution is known. Maleic acid, a-pinene, and diterpene are quantitatively hydrogenated by this method. However, only one of the two double bonds in dipentene and abietic acid becomes saturated under these conditions. Acknowledgment The writer is indebted to Jean Piccard for numerous helpful suggestions which were made during the progress of the work. Literature Cited [ l ) Adams, “Organic Syntheses, ’ Vol V I I I , p 10, R‘iley, 1928 ( 2 ) Albright, J. A m Chern S O C 36, , 2189 (19141.
117
(3) Armstrong and Hilditch, Proc. Roy. SOC.(London), 108, 128 (1928). ( 4 ) Boeseken, van der Weide, and M o m , Rrv. trav. chim , 35, 260 (1916). (5) Gough and King, Chemistry Industry, 47, 410 (1928). (6) Griin and Halden, Z . d e u t . Ol-Fett-Ind., 44, 2 (1924:; C. A , , 18, 1912 (1924). (7) Lochte, Bailey, and Noyes, J . i l m . Chem. SOC.,43, 2601 (1921). (8) Maxted, “Catalytic Hydrogenation and Reduction,” p. 22, Churchill, 1919. (9) Oppenheim, University of Lausanne Thesis, p. 13 ilE124). (10) Paal and Gerum, Ber.. 41, 813 (1908). (11) Parry, “Chemistry of Essential Oils,” Vol. 11, p . 331, Scott, Greenwood, 1919. (12) Piccard and Thomas, Ilelu. Chim.A c t o , 6 , 1045 (1923). (13) Reid, J . A m . Chem. SOL.,37, 2113 (1915). (14) Skita and Meyer, Ber., 45, 3595 (1912). ( 1 5 ) Stark, Ibid., 46, 2336 (1913). (16) Vorhees with Adams, J . A m . Chem. Soc., 44, 1403 (1C22) (17) Willstatter and H a t t , Ber., 45, 1472 (1912).
A Reductor Apparatus for Detecting Tin’ J. H. Reedy CHEMISTRY DEPARTHEST, UXIVERSITYOF ILLIXOIS,U R B A N AILL. ,
T
I S is generally detected in qualitative analysis by converting it into stannous chloride and testing for the latter by means of niercuric chloride. The second reaction Is known to be very sensitive, as little as 0.0001 gram in a volume of 10 cc. being easily detected. On the other hand, tlie rediiction of stannic tin to the stannous state is difficult and becomes quantitative only under cxrefnlly regulated conditions. The agents in most co111nion use for the qualitative reduction of stannic tin are the metals zinc, iron, and aluminum, acting in dilute hydrochloric acid. Lead has been suggested (?), but its action in the massive form is too slow to be satisfactory. Since the reduction takes place only a t the surface of the reducing metal, it is important that the solution should be brought into as intimate contact with the metal as possible. Evolution of hydrogen may interfere by forming a gaseous envelope around the metal, insulating it from the cations to be reduced. Treadwell ( 1 ) has shown that stannic tin can be quantitatively reduced to stannous chloride b y passing the solution, strongly acidified with hydrochloric acid, through a layer of specially prepared lead. This suggests that, by using lead in a modified Jones reductor, a new qualitative test for tin might he developed. -Plug of Cotton
Apparatus a n d Procedure
The apparatus (see figure) consists of a filtering column about 20 em. long, which may be easily made from glass tubing 1 to 2 em. in diameter. though a calcium chloride tube may be found quite serviceable. A plug of cotton or glass wool is placed in the bottom, and the tube is filled to a depth of about 10 cm. with pulverized (“test”) lead. The solution to be tested is acidified with about one-tenth its volume of dilute hydrochloric acid, giving a H-ion concentration of 0.5 to 0.6 S. The solution is heated to boiling and filtered through the reductor into a test tube containing 3 or 4 cc. of mercuric chloride solution. The liquid adsorbed in the Reductor Appar a t u s f o r Tin
1
Received December 9, 1929.
column is n-aslied out by means of 15 or 20 cc. of water colitailling 3 or 4 cc. of dilute hydrochloric acid. d precipitate of lead chloride may form in the filtrate, t u t it is easily recognized by its appearance and may be redissolved by Iieating. In case of doubt the precipitate is filterid out, washed with hot water containing a little hydrochloric acid, and treated with ammonium hydroxide, d blackening indicates mercurous chloride, and indirectly t,lie pr1:sence of tin. After use, the reductor limy be restored to wmking order by passing through it hot water, acidified by liytlrochloric acid, until the filtrate gives no turbidity with mercuric chloride. Usually about, 25 cc. is sufficient. There is no need of recharging a reductor until the upper half of the lead column becomes discolored or shows ot,her signs of deterioration. An occasional mashing with hot ammonium acetate solution is useful in removing lead compounds and renewing tlie active surface of the metal. Comparison with Other Methods
In order to compare the test in sensitiveness with other procedures, parallel t,ests were run with the usual zinc and aluminum methods. Results are shown in the following table: W T . OF IN
S n VOL-
SOLN. U M E Grain Cc.
0,001 0,0008 0.0006 0.0004 0.0002 0.0001
10 10 10 10 10 10
REACTIOXWITH HgCI? AFTER REDUCTION WITH: Zinc Aluminum Pb-Reductor Slight turbidity Doubtful Sone None h-one Sone
Slight ppt. Turbidity Doubtful None None Kone
Ppt. Ppt. Ppt. Turbidity Slight turbidity Doubtful
The weights of zinc and aluminum used in these tests were about 0.5 and 0.05 gram, respectively, the first, in the form of crystals and the second in the form of wire. I n both cases sufficient hydrochloric acid was added to cause a mild effervescence. Lead seems to be the only metal suitable for use in the reductor. Zinc and aluminum reduce tin salts to metallic tin, wliich is wholly retained in t,he column. Using iron, the reduction stops a t the stannous stage, but owing t o the removal of the free acid by the excess of iron the st,annous salts are hydrolyzed into insoluble forms, and the tin is again retained in the reductor. Lead, on the other hand, not only reduces bhe tin to the required valence, but has the additional advantage of being practically unatt:acked by dilute
.
L1-AL Y T I C AL EDI T I O S
118
acids. Since the test approaches so closely in sensitireiiess to pure stannous chloride, little or no tin can be lost by precipitation in the column. Discussion of Results
Except for interferences by a fern anions, this test for tin is specific, and can be used on the original solution with only a slight loss in sensitiveness. Among the cations, Cr7-T and NiTf are probably the most undesirable, since their color seems to obscure a faint mercuric chloride reartion. The metals occurring below hydrogen in the e. m. f. series are completely precipitated in the upper layers of the lead and, beyond increasing the amount of lead chloride that may go into the filtrate, are without effect. One milligram of tin in the presence of several hundred milligrams of copper, silver, etc., is easily detected. Even the combination of mercuric and stannic chlorides causes no complications. The mercury is completely precipitated in the upper layers of the column without any perceptible formation of mercurous chloride. Among the anions there are several that seriously interfere with the test. Iodides pass into the filtrate and react with
Yo1. 2 ,
so. 1
the mercuric chloride to form red mercuric iodide, which completely masks the presence of mercurous chloride. S i trates, chromates, chlorates, and other anions of oxidizing acids prevent the formation of stannous salts, particularly in solutions of high acidity. It was found possible, however, to detect 1 nig of tin in the presence of 2 millimols of sodium nitrate by keeping the acidity below 0.3 -1-and using cold solutions. Certain anions, as oxalate and phosphate, although they form insoluble salts with Pb'-, have no interfering action Even sulfate and sulfide do not seriously interfere. Ferrocyanide and ferricyanide, on the other hand, must not be present, since they produce turbid filtrates, green to blue in color. All of these interferences may be obviated by first evaporating the solution to dryness with an excess of hydrochloric acid. By this treatment these interfering anions are either expelled or destroyed, and in this way the test becomes available for solutions in general. Literature Cited (1) Treadwell, Hela. Chim. A c t a , 6, 816 (1922). ( 2 ) Treadwell and Hall. "Analytical Chemistry," To]. I, p , 254 11916)
Application of Burgess-Parr Sulfur Photometer to Rapid Determination of Sulfur in Foods and Biological Material' Edward W. Toepfer2 and Paul W. Boutwell BELOITCOLLEGE, BBLOIT, \VIS.
This paper describes a rapid routine method for deHE need for a rapid, ter to the determination of termining the total sulfur content of foods and biosulfur in foods and biological accurate method for the logical material. material, with the view to determination of total For the oxidation of materials of suitable character finding an accurate method sulfur in foods and biological up to 1 gram the Burgess-Parr sulfur bomb may be for routine work and one material is evident to all who safely used with the complete retention of the prodsuitable for experiments in have experienced the difficulucts. This method has advantages in ease and speed sulfur metabolism. t i e s of t h e u s u a l o f f i c i a l over the official sodium peroxide fusion. The application of the Burmethod. S t o c k h o l m a n d Oxidation with strong perchloric acid is applicable gess-Parr sulfur bomb and Koch (8) pointed out that in to biological material of all types, and is particularly photometer to the determinathe fusion of the sample with useful for large samples of low sulfur content. tion of sulfur in foods is suga mixture of sodium peroxide The sulfur in the oxidized sample may be quickly gested in the directions ( 2 ) acand sodium carbonate there determined by the use of the Burgess-Parr sulfur phocompanying the instrument, is some loss of sulfur. These tometer, which depends upon the formation of colloidal There is little in the literature writers developed a satisfacbarium sulfate. The conditions for operation must be to suggest that this method as tory method for the determicarefully controlled. applied to foods and biologination of total sulfur in which cal material has been tested the oxidation is effected by the use of 30 per cent hydrdgen peroxide, followed by fuming to any extent. Latshaw ( 5 ) and LeClerc and Dubois (6)used nitric acid and bromine water. Barlow ( I ) earlier called the Burgess-Parr bomb in place of the official sodium peroxattention to the loss of sulfur in the usual dry fusion methods, ide fusion with success, but they followed i t with the usual and also in the wet methods of oxidation which he studied, gravimetric determination of the sulfur. As these investiand developed a combustion method for the Oxidation of gators point out, the utility of the bomb is limited b y its the sample, which, although reliable, is not suitable for rapid capacity and when the sulfur content is low it is often imroutine work. Many modifications have been suggested possible to oxidize a sample large enough to insure a sufficient both for the preliminary oxidation and for the final determi- weight of barium sulfate for a satisfactory determination. nation of the sulfur. S o attempt will be made to give a We have found that samples up to 1 gram can be safely oxicomplete review of this literature. It was the purpose of dized in the special 5.08-em. fusion cup furnished by the the work here reported to study the application of the Bur- makers. When a low sulfur content makes necessary the gess-Parr sulfur bomb and the Burgess-Parr sulfur photome- use of larger samples, it has seemed better to resort to another method of oxidation. The development of a larger bomb Presented before t h e Division of Agri1 Received October 2 , 1929 cultural and Food Chemistry a t t h e 78th Meeting of the American Chemical to handle safely from 2 to 3 grams of material would be very Society, Minneapolis, Minn , September 9 t o 13, 1929 desirable. The use of the bomb has much to its advantage. 2 This paper is p a r t of a thesis presented by Edward m' Toepfer a t It is easily assembled. The charge may be electrically igReloit College for the degree of master of science
T
