294
ANALYTICAL CHEMISTRY Table VII.
Average Results, Repeatability, and Reprodtrcibilit! (.%.S.T.lI. acid a n d base nuiiiber coolieratire Yurrey)
~. .d.S.T.M. D 664
.%vera~e result
Sample
.%.S.T.11.D 663
Repeat- Repro- .%\.wage ability ducibility result
RepeatReproability ducibility
a-Saplitiiolbenzein _-__ Alkali Blur Average RepeatRepro- Average RepeatReproresult aiiilits. ducibility result ahilits. ducihility
4-47 5-47 6-47 7-47 8-47 9-47 10-47 11-47 12-4: 13-47 14-4i
.\cid S o . Magnitude S ~ i r v e s .iiiax. 4-47
A.S.T.11. spec.
to fi-47
0.0-0.73
(I.
n
n
02
(i IIU$
0 00i
0.03
I1 03
0.01 0.05
I1 09 01.5
037
Survey niax. 7-47 i o 14-47 .\.S.T.AI. spec.
0 29 i3.iVc of
Table V l l l .
Saponification Tendencj of Test \lethods A.S.T.hI. 13 662-46T
A S T.11. D 6fi3-4RT
Aciiial 14-47
2.94
1 .,i6
2.45
Calculated 14-47
1.80
1 .45
2.41
I 87
Ilifference
(1.14
0.11
0.04
0.13
a-Naphtholbensein
ilkall Blur "00
the amount of saponification taking place is invariably raised. In Tables V I and VI13samples 13-47 and 14-17 were prep:~i'edto d(Jtermine this point. Sample 14-47 is the same oil as sample 13-47. to which was added 10% of prime lard oil having an acid number of 0.5. Because these weak acids blend arithmetically, Table VI11 has been prepared t o show the actual results obtained on 14-47 :rnd those calculated from the blend of 13-47 and the lard oil. It is possible that snponification did not cause all the inci~~:tuc~ in view of the repeatahility and reproducibility of the tests. However, the fact th:it the deviations were constant in one direction indicatrd that a small amount of saponification did take place. The results obtained by the a-naphtholbenzein method \wre ill wrprisingly good agreement, SCWMAHY ~ N CONCLUSIOS D
Thousands of cooperative tests during the past several yc':ii's have indicated that no satisfactory method of determining thr :iridic 01' basic romponenta present i n petroleum luhricxting oils
Ijy tno-phase titration i s :rv:iilable. Two single-phaw titration methods rvere found which showed considerable promise. and their development h:ts r r d t e d in simple arid fast methods of improved precision. The method using a-naphtholhenzein was :idopted because it more consistently gave results similar t o thosc. obtained with the (llcctrometrir titration. 4 C KNOF'L E1)GME.V'~
The author is pitrticwlarly indebted to the laboratories of General 1Zotors Research, Shell Development Company, Standard Oil Company (Indiana), and Standard Oil Company (Ohio) for carrying out the vast analytical program covered by this paper. He also wishes to express his appreciation to Louis Lykken, IT. E. Scovill, E. B. Tucker. and H . R . \Volf for tho many hours spent in developing this program, xi(t t o H. 1'. T,ankrlmn for his careful review of the manuscript. L I T E R 4 T C R E CITED
(1) Ani. Soc. Teatiug Materials, Standard*, 1911 S i i p p h * i e r i t , Pai,t 111, p . 302. (2) Ibid., 1944, Pai,t 111, p . 1198. (3) Ibid.. 1946, Part III-;\. p. 819, D 664-46T. (4) IDid.. p. 824. ( 5 ) Lykkeri, Porter, ltuliffson. and Tueiriiniei~,I s i i . Ksi,. ( ' H E M . , AS.AL.ED., 16,219 (1944). K E c e r v E o 3Iarcli 28, 1949.
Determination of Total Phosphorus in Organic Phosphates W . K. S l \ l \ l O X S
T
41VD ,J. H. ROBERTSON, I.nicersity of Tennessee, finoxr%ille,T e n n .
HE extensive use of organic phosphates as insecticides and for other purposes necessitates a satisfactory method for their chemical analysis. .4s a basis for rating the insecticidal value of an organic phosphate mixture, a selective method such :is the one proposed by Dvornikoff and hlorrill(4) or the method proposed by Wreath and Zickefoose ( I O ) for the determination of tetraethyl pyrophosphate, which is the active insecticidal agent i n certain organic phosphate products, is of prime importance, but t,his excludes other formr of phosphorus which may contribute to the value of the product as, for example, by increasing the total phosphorus uptake by plants (8). Jacobson and Hall ( 7 )adapted an alkali fusion method to the conversion of organic phosphorus in aliphatic phosphates, then determined the phosphorus colori-
metrically by the mol?-bdivanadophosphoric acid method. The>found that the method is rapid and accurate and that it involves , they repnrted no data negligible damage to platinum ~ w r e but for aromatic phosphates. Hardin and IIarIiitire ( 6 ) demonstrated t h a t whereas the official A.O..4.C. procedures register the full phosphorus content of all tested fertilizers, those procedures register 011ly fractional values for certain concentrated organic phosphates. They SUCceeded in transforming the phosphorus in hesaethyl tetraphojphate to ionized orthophosphate by digesting an aliquot that contained 0.04 gram in 10 ml. of water with 5 ml. of hydrochloric acid and 5 ml. of nitric acid for a period of 16 hours a t 120" C. Prolongation of the digeytion period to 21 hours effected complete
V O L U M E 2 2 , N O . 2, F E B R U A R Y 1 9 5 0
295
'I'M o independent procedures for the contersion of organic phosphorus into ionized orthophosphate are adapted to the \olumetric determination of phosphorus by the molybdiphosphate-alltalimetric method. One procedure is based upon the reaction with hydriodic acid; the other is based upon destructite oxidation with a mixture of nitric, perchloric, and sulfuric acids in the presence of a mol) bdenum catalyst.
conversion of triethyl phosphate and monoethyl phosphate, but r l r i l > . partial convrrsion of t a o samples purported to be tritolyl 111ioaph;rtc~and triphenyl phosphate. it-reath (9) has reported t11c us(' of perchloric-nitric acid mixtures on some samples of organic phosphates after first checking the results against those ol)tainetl by Parr bomb combustion. In the present paper two tlistirictive method9 are presented for the conversion of organic. phosph:ites, both diphatice :rnd aromatic, and i n each case the i h completed by thrb .\.O..\.C. molyl~tiiphoaphate-alkaliitrution procedure ( 1 i. The first method is Imscd upon reaction with concentrated liydriotlic acid. S o attempt to use this reagent in the analysis of c~rganiephosphates has heen reported. Its possibility was indic a t i d ))? the results ol)tainccl 1)y Flew?-, Courtois, and Drsjobert ~~
Talde I .
(5) in their rtudy of the rates of hydrolysis of ethyl and glycol phosphates. They found that for a given normality (1 to 10 *V) the rate of hydrolysis increased with the presence of the arid i i i the order sulfuric, hydrochloric, hydrobromic, and Ii>driodic. The second method is biiaed upon oxidation with a mixtures of perchlorir, sulfuric, and nitric a d s i n the presence of sodium molybdate as a catalyst. .\lthough this method for the decomposition of orgtrnic. phosphates has not been reported, it has been proposed l>>. Roliri and Stambery (31, but without the addition of' nitric :irid, for the analvsis of various agricultural feed materials. SPECIAL REAGENTS
spFc+icgravity 1.7, 5 5 , 58%. Hydriociic aciti, c,l,, Sodium nioly~)ciat~.-sulfuricarid-perchloric acid oxidation mixture. Dissolve 35 grams of ._ - ._ sodium molybdate dihydratei n 160 ml. of water. Add I50 nil. of conccntrated sulfuric3 t f ? driodic -icitl Conversion of Phosphorus in Aliphatic Phosphates acid and 200 ml. of conceriP.05 Content by Molybdiphosphate-hlkaliinetric Method, -~ . tratcd pc~rohloricacid. Tetra~
~~
R e H r i Y I'eri~id 51 ith Hydriod!c. .irid. Hoiir.
Hem(xth>-l tetra
_- _- -
Hrsaethyl tetra
Monoethyl
1Ionoethyl
ethyl
pyro
base" 48.3 48.3
Tributoxs ethyl 16.Yc 17.5 17 17.t 17.5 17.6 li.3 li.3
Triethyl 37.6 37.7 37.6 38.1 37.9 37.8 2
Vapotoneb
Triethyl 38.3 37.8 37 2
PROCEDURE
Hydriodic Acid Conversion' 0 08 Keigh 0.25 to 0.30 gram of or0 , 2
