A Micro Method for the Estimation of Ethylen in Ripening Fruits. 145

gearbeitet, die es erlaubt, Spuren yon Athylen, das von reifenden Friichten abgegeben wird, qualitativ einwandfrei nachzuweisen. Die Methode gestattet auch eine gleichzeitige quantitative Sch~tzung des Athylens.

Luft wurde durch mit reifenden Bananen geftillte und abgedieh- fete Beh~ilter gesaugt und die aufgenommeneaen Spuren Kthylen- gas in entsprechenden Absorptionsapparaten in Brom absorbiert. Das so gebildete Athylenbromid wurde in einer dem PRF.CL'schen Mikromethoxylapparat nachkonstruierten Vorrichtung durch Be- handlung mit alkoholischem Kali, in Azetylen umgesetzt und die- ses als Kupfer- und Silberkarbid gefi~llt. Letzteres wurde abfil- triert, gewogen und dann mit Salzs~iure umgesetzt. Das so ge- bildete Chlorsilber wurde wiederum gewogen. Die auf diese Weise erhaltene quantitative Beziehung zwingt zur Schlul~folgerung, dal~ ~thylen in der Atmosph~ire yon reifenden Bananen vorhanden sein Inu]~.

Die Menge Kthylengas, die yon reifenden Bananen gebildet wird, bewegt sich zwischen 0.1--0.2 cc 3, gemessen unter Normalbedin- gungen per 45 kg Frfichte. Da diese Menge Athylen in 6000 Liter Luft enthalten war, muBte ein Tell aus 10 Millionen Teilen isoliert werden.

AN IMPROVED MICRO-KJELDAltL METHOD FOR THE DETERMINATION OF NITROGEN IN COALS.

By

A. E. Beet and R. Belcher.

Department of Fuel Technology. The University of Sheffield.

(Eingelangt am 5. Februar 1938.)

The analysis of coal by means of micro-analytical methods has not received the attention it deserves, because many workers consider that sampling errors are likely to occur when using small quantities of such a heterogeneous substance. One gram is the amount generally used in most of the standard methods of coal analysis, although for the determination of carbon and hydrogen, 0.1 to 0.2 gram only is used. I t is obvious, therefore, from the accurate results obtainable by the latter determ, ina~ion, that

10

146 A. E. Beet and R. Belcher:

serious sampling errors would not occur if weights of about 100 rag. were used in any coal analysis, and it is probable (assuming that the original sample has been correctly sampled and mixed) that accura,te results are obtainable with even smaller quantities.

Until the introduction of selenium as a catalyst the digestion period required by coals was about 8 hours. This period was reduced to about 2½ hours by using a mixed catalyst of selenium and mercuric sulphate. By applying micro-analytical technique to the method now used in this Department for the estimation of nitrogen in coal 1 the following modification has been evolved, which is equal in accuracy to the macro-method and achieves a considerable saving of time. The whole determination may be completed within 30 minutes.

(i)

(ii)

(iii) (iv)

(v)

(vi) (vii)

(viii)

M a t e r i a l s r e q u i r e d .

The coal ground to pass a 72 B.S. sieve (11120 inch aperture). The catalyst mixture composed of 32 parts by weight of potassium sulphate; 5 parts by weight of mercuric sulphate; and one part of selenium. The components should be finely powdered and intimately mixed. Pure nitrogen-free sulphuric acid. A solution of caustic soda and sodium sulfide for preci- pitating mercury. To 9 volumes of 40% caustic soda is added 1 volume of 40% sodium sulphide solution. A saturated solution of boric acid (about 40 grams per litre) L A centinormal solution of hydrochloric or sulphuric acid. An indicator prepared by dissolving 0.125 gram of methyl red and 0.083 gram of methylene blue in 100 cc. of absolute alcohol. This is violet when acid, green when alkaline and has an intermediate blue stage 3 ,,Perhydrol", concentrated chemically pure hydrogen per- oxide "Merck".

1 Fuel 13, 343 (1934). 2 L. WINKLEII, Z. angew. Chem. 26, 231 (1913).

JOHNSON and GREEN, J. Ind. Eng. Chem., Analyt. Edit. 2, 2 (1930).

A Micro Method [or the Determination of Nitrogen in Coals. 147

P r o c e d u r e .

100 mg. of coal are weighed on a counterpoised scoop using an ordinary chemical balance, and transferred to a digestion flask. About 1 cc. (1 g.) of catalyst mixture is measured in a dry measuring cylinder, and added to the coal with shaking in order to mix well. Three cubic centimeters of concentrated sulphuric acid are added and the flask heated over a micro-burner. In about 8 to 10 minutes the contents of the flask will have cleared to a pale lemon colour. This stage may be reached in 4 to 6 minutes by the addition of a few drops of Perhydrol. The boiling is continued for a further 15 min. after the contents of the flask have cleared, to ensure complete conversion of the nitrogenous bodies to ammonium sulphate. The digestion is then complete. For the distillation we use a larger form of the PaECL distillation apparatus (distillation flask has a capacity of 150 cc.) fitted with a suck-back device as in the PARNAS-WAGNER apparatus and a transparent silica internal condenser tube. 10 cc. of the alkali-sodium sulphide mixture are run into the distillation flask via the tap funnel and the latter well washed with distilled water, 2 cc. of boric acid solution are run into the receiver from a burette, 3 drops of the indicator added and the flask placed so that the condenser tube dips below the surface of the liquid. The diluted digest and washings are then introduced into the distillation flask and the tap funnel again well washed. The distillation is allowed to proceed during 5 min.

T a b l e I.

Micro-method using Macro-method using 0.1 g. coal. 1.0 g. coal.

Coal. Average of 4 results Average of 4 results °/o N o/0 N

Lignite (Bovey Tracey) Lignite (Iceland) Bituminous A Bituminous D BRuminous (South Africa) Bituminou~ (Nostell Winter Semi Bituminous Anthracite (South Wales) Anthracite (Red Vein)

0.34 0.50 1.62 1.46 2.22 1.73 1.22 1.18 1.39

0.33 0.50 1.60 1.47 2.21 1.72 1.23 1.20 1.39

10"

148 Ch. Cimerman et P. Wenger:

and then for 1 minute with the receiver about 1 inch below the end of the condenser. The distillate is then t i trated with the N/100 acid until the indicator assumes the intermediate blue stage.

Each cc. of N/100 acid ~ 0.14~ N, using 0.1 gm. coal. A largo range of coals has been analysed by this method and compared with the analyses obtained by the macro-method. A representative few of these results are recorded in Table I.

E T U D E M I C R O A . N A L Y T I Q U E DU ZINC A U MOYEN D E

L ' O - O X Y Q U I N O L E I N E I.

Par

Ch. Cimerman et P. Wenger.

Laboratoire d'analyse microchimique de l'Universit6 de Gen6ve.

(Eingelangt am 21. Februar 1938.)

I n t r o d u c t i o n .

L'o-oxyquinol6ine introduit en analyse par R. BERG I e t FR. L. HAHN ~" s'est montr6 un r6actif tr~s f6cond. I1 suffit, en offer, de ~eter un coup d'oeil sur la monographie de R. B~.BG 3 pour se rendre compte du grand nombre de m6thodes 6tablies au moyen de ce r6actif.

Nous avons fait une 6tude approfondie de micro-dosage du zinc quo nous exposona en trois parties:

Premier article: Le micro-dosage gravim6trique.

Deuxi6me article: Deux micro-m6thodes volum6triques (on milieu ac6tique et on milieu alcalin).

Troisi~me article: Los micro-s6parations du zinc d'avec une s6rie d'616ments usuels.

1 Journ. prakt. Chem. 115, 178 (1927). 2 FR. L. FfA~N, Ztachr. angew. Chem. 39, 1198 (1926); FR. L. HAHN et

K. VL~WEC, Ztschr. analyt. Chem. 71, 122 (1927). 3 Das o-0xychinolin. Verlag F. Enke. Stuttgart 1935.