Free carbon was determined in silicon and boron carbides in ash, oxides, and other materials by oxidation to carbon dioxide with a mixture of K2Cr2O7 + H2SO4. The determination was made from the amount of CR(6) consumed, by adding excess Mohr's salt and titrating with a standard solution of KMnO4. The amount of Cr(6) self reduced was determined in a blank test. Optimum oxidation and conditions were achieved when the volumes of 5% k2Cr2Oz and H2SO4 were equal. The mixture was boiled for 1-2 hours using a reflex condenser. The volume should not be reduced, in order to avoid an increase in the sulfuric acid concentration. The relative error was 4-7% for 0.005-0.04 g C and less than or equal to 3.5% for 0.1 g C

Kuteynikov, A. F.

Mashkovich, L.

English

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NASA TM-75259
NASA TECHNICAL MEM JiDUM...... 

DETERMINATION OF CARBON BY THE OXIDATION-REDUCTION REACTION
 
WITH CHROMIUM
 
L. Mashkovich and .A. F. Kuteynikov 
NAA-Tm-7526 9) DETERMINATION or CARON B 10F-19230 
TN OIA IREDUCTION REACTION wITH 
CHROMIUM jNational Aeronautics and Space
Administration) 9 p HC A02/Mr A01 CSCL 07D /508653
 
Translation of "Opredeleniye ugleroda p® okislitelno­
noy reaktsii s khromon", In: "Sovremennye
vosstanovitel t

metody khimicheskogo i spektralnogo analiza materialov,
 
(Modern Methods of Chemical and Speetral Analysis of
 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
 
MARCH 1978
WASHINGTON, D.C. 20546 

https://ntrs.nasa.gov/search.jsp?R=19780011287 2020-03-22T06:04:47+00:00Z
STANDARD TITLE PAGE 
1. Report No. G2.overnment Accesson No. 3. R cpent's Catalog No. 
NASA TM- 52 
 
4. Title and Subtitle _5. Report Dote 
DETERMINATION OF CARBON BY THE 0XI- 6 Prnrni C
DATION REDUCTION REACTION WITH CHROMI C' Performing0Oganization Code 
7. Author(s) 8. Perforning Organization Report No.L. Mashkovich and,./ A. F. Kute~nikov-- i 
10. Work Unit No. 
11. Contract or Grant No.9. 'Performing Organizat.on Name and Address NASw-2790 
Leo Kanner Associates, 
-Redwood City, 13. Type of Report and Period Cover.ed 
California 94063 
 Translation 
12. Sponsoring Agency Name and Address 
National Aeronautics and Space Admini-14. Sponsoring Agency Code 
stration, Washington, D.C. 20546


15. Supplementary Notes _ _-­ fl 
Translation of "Opredeleniye ugleroda .po okisliteltno-

T vosstanovitelney 
 reaktsli s khromon", In: Sovremennyye
metody khiicheskogo i spektral'nogo analiza materialev,


_--9._ _pp,._2LT_220__(Modern Methods of Chemical and Spectral Analysis of Materials)


16, Abstract 
Free carbon was determined in silicon and boron carbides


in ash, oxides, and other materials by oxidation to carbon
dioxide with a mixture of K.CrA0

7 + H.SO 4 . The determin­

ation was made from the amount of Cr(VI) consumed, by

adding excess Mohr's -salt and titrating with a standard 
solution of KInOq. The amount of Cr(VI) self-reduced was
determined in a blank test. 
 Optimum oxidation conditions


were achieved when the volumes of 5% KjCrO and HOS0q 
were equal. The mixture was boiled for 1-2 hours using

a reflex condenser. 
 The volume should not be reduced, in

order to avoid an increase in the sulfuric acid concen­

tration, The retlative. error was 4-7% for 0.005-O.O4.g

C and - 3.5%for 0.1 g C. 
17. Key Words (Selected by Author(s)) 18. Distribution Statement 
Unclassified-Unlimited


19. security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 
Unclassified Unclassified 
NASA.HO 
DETERMINATION OF CARBON BY THE OXIDATION-REDUCTION REACTION


WITH CHROMIUM


L. Mashkovich and !A. F. Kutae5nikov 
A method is developed for determining carbon /217* 
according to the reaction with a mixture of potassium 

bichromate and sulfuric acid, by means of the deter­

mination of reduced chromium. The method,is used for


determining carbon in iaterials containing boron car­

bide, silicon carbide, and fluoroplastic.


In order to determine free carbon in materials containing 
chemically stable carbides, methods are used which are based 
on the capability of free carbon to be oxidized to a dioxide 
by various oxidants and mixtures of them Ei]. 
Corleis developed the principle of the method of damp 
oxidation of carbon and used it to determine combined carbon. 
The procedure is based on the dissolving of cast irons, steels, 
iron, and ferroalloys in a mixture of H SO9 + CuSOq + HCrOQ 
with the absorption of C0. by soda lime [2]. The mechanism 
of the reaction is expressed [2, 3] by the equation 3C + 
2K±CrpO 7 + 8HSO = 2K1SO1 + 2Cra(SO) 3 + 3C0O + 8HO. 
Carbon black, coal, coke, and graphite behave differently


toward oxidants, with graphite being the most stable.


We tested the oxidizing capacity of a number of mixtures


with respect to different types of graphite and to the


compounds which are contained in the materials being studied.


+ Kra 2 OpIt was established that the chromium mixture H SO 
 
*Numbers in the margin indicate pagination in the foreign text.


±


is the most suitable., It oxidizes carbon completely and does


not affect silicon carbide, boron carbide, fluoroplastic,


ash, oxides, and silicon. The chromium mixture was used


earlier [4, 51 for oxidizing free carbon in B#GC, with


absorption of carbon dioxide by asbestos or barite.


We propose a method for determining carbon, based on


the determination of the chromium consumed in oxidation.


The method was tested on spectrally pure graphite, using


a mixture with various chromium and sulfuric acid contents


for oxidation. An increase in acidity acelerates the process


of oxidation of the carbon (Fig. 1), but at the same time /219


assists self-reduction of the chromium (Fig. 2). This


phenomenon was observed in a blank test, i.e. through heating


of the mixture without carbon. Self-reduction of chromium


disturbs the stoichiometric character of the reaction and


causes errors in the determination of carbon by chromium.


Comparison of the obtained results made it possible to


establish the optimal composition of the mixture and the


oxidation conditions under which the oxidation-reduction


reaction between carbon and chromium occurs stoichiometrically.


This mixture should consist of a 5% solution of potassium


bichomate and concentrated sulfuric acid in a 1:1 ratio. An


increase in the chromium concentration, with heating and


subsequent cooling, leads to the precipitation of KCrO 7


crystals. It is necessary to conduct the heating without


reducing the volume, so as not to increase the sulfuric acid


concentration.


The given mixture oxidizes 1 g of graphite in 2-2.5 hours.


In this case, the amount of self-reduced chromium is n0.3%.


Taking this amount into account according to a blank test,


one may preclude error or reduce it to a minimum.


2


/218 
Or 
0 
2 
cI 
.rdX 'gFig.
o 
3 
1. Dependence of the 
rate of oxidation of free 
H 
4f 
o 
o 
-P_ 
O3'f6058, do ,ol 
carbon on the sulfuric acid 
concentration in the chromium 
mixture: 
1-0.01 g CF, 2-0.05 g
Cr, 3-1.00 g CF 
•H 
E-i 
(:4 1:2 
IHZSOq 
'I .2:/ 4:! 
KrrZo7 
00 
JO 
2 
t, hrs.
 

Fig. 2. Effect of boiling time and composition

of chromium mixture on the reduction of chromium


in the blank test. Curves 1-4 correspond to the


ratio of H.S0q (1.84): 10% KCr.0y = 1:4; 1:2; 
1:1; 2:1.


3 
Given in Table 1 are the results of determining spectrally


pure carbon using chromium. The relative error of determination


was 4-7% for 0.005-0.04 g C and 43.5% for 0.1 g C. The time


of a single determination was 20-30 minutes. This method makes


TABLE 1


RESULTS OF THE DETERMINATION OF CARBON ACCORDING TO


THE OXIDATION REACTION WITH CHROMIUM (n=10)


b


a KoanqCcTBo 
______________e, HaflAeno C OMnCOa 
Cp~ia CL X2 
P CHn %(OTHo) 
no pCaKwHH HaMED 
5,0 28,9 30,5 53 5,6


10,0 57,8 58,7 10,2 2.0


20id 115,7 118,1 20,4 2,0


40,0 231,1 231,6 40,1 0,25


60,0 346,7 344,3 60,0 0


80,0 462,2 449;7 77,8 2,75


100,0 577,8 579,0 100,2 0,20


Key: a. Amount of graphite, mg d. Found


b. Consumption of Cr(VI), e. C found, mg


mg f. Error, % (relative)'


c. Calculated according to


the reaction


it possible to determine from several to dozens of per cents


of carbon, and maybe recommended for the analysis of materials


containing oxides, ash, silicon, fluoroplastic, boron carbide,


and silicon carbide.


A 0.1-2 g sample of the material, finely divided to -150


+200 mesh, was processed by boiling with a 5% solution of


potassium bichromate, accurately measured with a buret, and


with the same amount of concentrated sulfuric acid. The


processing was conducted in a conical flask of 200-300 m2


volume with a ground refluxtcondenser for 1-2 hours. A blank /220


test was performed at the same time. After dissolving, the


4 
contents of the flask, with the precipitate, were transferred


to a 250 m) volumetric flask.
 

If necessary, the precipitate was filtered through a


glass filter and weighed.


A 0.05 n. solution of Mohr's salt, the excess of which was
 

back-titrated with 0.05 n. potassium permanganate, was added


from a buret to the aliquot portion (25/250 for the sample


and 5/250 for the blank test) [6]. The carbon content was


calculated according to the formula


- 100 
X= 5,78a 
XA 
where tL is the sample in g; 5.78 is the amount of Cr(VI) going


into the oxidation of 1 g of carbon; A is the amount of Cr(VI) 
going to the oxidation of C, in the sample; A=B -B (B. and 
B are the amounts of Cr(VI) taken for oxidation and remaining 
after oxidation of carbon).


The developed method was tested on artificial mixtures
 

and production samples. The most reliable results were obtained


with a content of > 1% C in the sample. The results are given


in Table 2.


TABLE 2


RESULTS OF DETERMINING FREE CARBON BY DIFFERENT METHODS


-b ­ Ha-Aeno .. ~.% 
HcCAeAyeMwf1 MaTCpHaJI ° nPeAaaraeMm SllrlHlBUM0¢0M0uTofOM r 6seRWo OAGM[6] 
jap6nA 6opa ........ . . . . 18 10,60 - 10,07 
rpa(PHT + SIC: 
12.. ...... - ,34 1,20 1,27I i....
-2 ........... - 61,47 61,10 ­
.N 3 ........... 
N2.4 ........... 
-
-
X2 5 .... ........... 
0,1 a SiC--0,1 a C ..... 
0.18 a SIC+0,02 a C .... 
-
.50 
10 
B-Si-C .... .......­
cr>oponJrac . ...... 
0TopO IJaCT ± rpa)1T:09e+0,1IaC........ 
0 
10 
092 a+0.O8 eC........ 8 
1 
61,08 
67,02 
81,44 
50,10 
10,13 
63,75
63,38 
0 
9,86 
7,94 
60,50 
67,7 
82,1
50,0 
9,85 
44,82 
-
-
.. 
-
-
-
9,96 
62,62 
65,81 
-
-
I 
N. I 
X9. 2 
X2 3 
........... 
... z......... 
..... ;..... 
50 
50 
65 
50,30 
52,10 
66,80 
. 
-
-­
-
5 
Key: a. Material being studied f. By the gas volume


b. C content,, % method L6]


c. C- found, % g. Boron carbide


d. By the proposed method h. Graphite + SiC


e. By the roasting method i. Fluoroplastic


j. Fluoroplastic + graphite


REFERENCES


1. 	 Analiz tugoplavkikh soedinenii [Analysis of High-Melting-

Point Compoundsj, Metallurgizdat (1962).


2. 	 Corleis, E., Stahl und Eisen, 14, 1894, 589.


3. 	 Lendel', G., et al., Analiz ,chernykh metallov [Analysis of


Ferrous Metals, Goskhimizdat, 182 (1934).


4. 	 Meerson, G.A., Samsonov, G.V., Zavodskaya laboratoriya 
XVI/2 (1950). 
5. 	 Kitakhara, Asakhara, Atodi, RZhKhii, No. 78324 (1959).


6. 	 Dymov, A.M., Tekhnicheskii analiz rud i metallov [Technical

Analysis of Ores and MetalsJ, Metallurgizdat, 194 (1949).


7 


Determination of carbon by the oxidation reduction reaction with chromium

Abstract

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