T H E J O C R X A L O F I N D G S T R I A L A N D ENGINEERIiL'G C H E M I S T R Y
J u l y , 1914
portional t o yield of fiber. This latter is also shown b y Nos. 2 , 8, 2 1 a n d 22, where yield is fairly regular a n d specific gravity is irregular. This would indicate t h a t habit a n d environment have much t o d o with t h e quality of wood. 11-We can establish very well t h e influence of incipient decay upon t h e yield b y comparing Kos. 1 2 , 1 7 a n d IS, all of which are sound specimens, with h-os. j, 4, j a n d ti; t h e annual ring growths compare
j61
averages about 48 or 7 5 per cent, showing t h a t t h e voids in 2 feet wood are less t h a n in 4 feet wood. Comparing t h e solid cubic feet we find i t t o be about I O O in t h e case of 2 feet wood a n d 9 j in 4 feet wood. F r o m experiments not shown here, i t has been proven t h a t large wood contains more solid wood per cord t h a n small sizes, in t h e ratio of about 96 t o 9 2 . F r o m these results i t is apparent how i m p o r t a n t i t is t o t h e manufacturer of chemical pulp t o know
TABLEI - ~ I O N T M O R E N CWOOD Y TEST(NOVEMBER. 19 12)
S O .
1 2 3
8 9
10
11 12 13 14 15 16 17 18
1Y 20 21 22 23 24
Sp. gr. of wood Rings per dried a t DESCRIPTIOS OF S A M P L E Diameter inch 100' C. 2 FT. \VOOD-lO0.3 SOLID FT. PER C O R D Sound, fine g r a i n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10" 23.3 0.4700 Sound, fine g r a i n . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 21.4 0.3522 Dead wood, medium coarse.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SI/? 14.1 0.3697 of center d r y r o t well established.. . . . . . . . . . . 13.1 0.3535 of center d r y r o t , p o o r . . . . . . . . . . . . . . . . . . . . . 15.6 0.3518 of center d r y r o t , very p o o r . . . . . . . . . . . . 15.4 0.3474 ne grain, slight indication of dry rot surfa 24.4 0.4141 .................................... 19.2 0,3076 6.8 0.3475 Sound, very coarse g r a i n . , . . . . . . . . . . . . . . . . 10.7 0.3365 Coarse grain, slight indication of d r y rot su Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 0.3242 Coarse grain, s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 0.3166 16.3 0,3469 D r y r o t and dead throughout, poor. . . . . . . . . . . . . . . . . . . . . . . . Coarse grain, d r y rot well established t h r o u g h o u t . . . . . . . . . . 5 ?/iz 10.2 0,3242 Coarse grain, s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 12.0 0.4094 5 12.5 0,3347 Coarse grain, dead wormy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 F T . \VOOD-95.64. SOLID FT. PER CORD l l e d i u m fine grain, s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5l!, 15.3 0.4011 Coarse irregular grain, dense, s o u n d . . . . . . . . . . . . . . . . . . . . . . 8112 12.9 0,4333 Coarse grain, rather light, s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . SI/, 12.0 0.3556 Coarse grain, s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 12.0 0.4291 Fine grain, s o u n d , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . il/z 19.7 0.3597 Irregular grain, medium dense, s o u n d . . . . . . . . . . . . . . . . . . . . 7 18.2 0.3651 Very fine grain. dense, s o u n d , , . . . . . . . . . . . . . . . . . . . . . . . . . . 101/z 24.0 0.3391 Very fine grain, light s o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 23.0 0.3368
favorably a n d yet t h e specific gravities a n d yields of t h e latter are noticeably low. 111-The most i m p o r t a n t conclusion of all a n d t h e one we are perfectly safe i n drawing is t h a t there is great variation in t h e yield of chemical pulp a n d t h a t some consideration should be given t o this yield i n fiber in valuing wood for pulp. T h e yield per cord is found b y taking t h e solid volume which t h e a u t h o r has found t o be a b o u t I O O CU. f t . a n d multiplying b y . t h e specific gravity. This gives t h e cord veight basis from which t h e yield i n fiber can be calculated. T h e volume yield is found b y multiplying t h e specific gravity into t h e percentage fiber yield. T h e specific gravity of wood is very quickly determined approximately b y displacement in mercury instead of water.
---
T h B L E 11-MONTMORENCY WOOD
TEST (NOVEMBER,1912)
lveight of Area in one cord one cord Lbs. Moisture +--Actual P e r cent per cent W-et Dry sq. f t . total 2 FT. WOOD 40.1 3990 2392 ... ... 43.3 3992 2220 .., ... 38.4 3636 2240 49.4 77.2 38.4 3616 2228 48.5 74.8 48.5 4395 2140 51.65 80.8 48.. 4255 2075 51.15 79.8 24 44 31 00
3014 3313
2277 2286
4 FT WOOD 24.22 75 70 23.60 73 75
Volume in one cord
Actual cu. ft.
.. 9i:S 97.0 103.3 102.3
No. of Per c e n t sticks in total
one cord
. . . . . .
. . . . . . 77.2 74.8
80.8 79.8
178 185 210 184
Per cent by weight
Per cent b y volume
Lbs. per per cord
51.6 51.5 49.5 47.2 52.3 48.2 52.8 53.5 55.2 54.1 53.9 52. I 41.6 4:. 2 54.0 49.2
24.2 18.1 18.3 16.7 18.5 16.7 21.9 16.4 19.0 18.2 17.5 16.4 14.4 15.3 22.1 16.5
1515 1132 1144 1045 1157 1045 1370 1026 1189 1139 1095 1032 901 957 1383 1032
55.0 54.5 56.1 57.2 53.0 51.6 57.5 59.0
22.1 23.6 19.9 24.5 19.1 18.8 19.5 19.9
1383 1477 1245 1533 1195 1177 1220 1245
what his wood will yield a n d for his purposes i t should be valued accordingly. Progress in valuing wood in a n y other way t h a n b y t h e cord unit mill be slow, because all timber having a dimension lumber value will necessarily be valued b y dimension. Again, as wood finds various markets, i t will be valued according t o t h e use i t is p u t t o in t h e highest market a n d t h e tendency t o value all wood b y t h e unit measurement of t h e principal market will persist. hIeanwhile conditions are rapidly changing whereby t h e poorer grades of wood only are finding their way t o t h e pulp mills a n d t h e question of supply a n d demand are determining factors. So far as t h e a u t h o r knows, manufacturers of pulp have done little or nothing t o promote a better standard of valuing wood for their uses a n d we m a y expect no change until t h e y t a k e this m a t t e r more seriously in t h e interest of more efficient management of their plants. RUMFORD, MAIKE
DETERMINATION OF CARBON IN SOILS AND SOIL EXTRACTS By J. W. AXES
AND
E. W. GAITHBR
Received April 6, 1914 96 88 94 40
i5.70 73.75
80 109
Table I1 shows t h e weights per cord of mixed spruce fir containing different percentages of moisture a n d t h e d r y weight, which averages a b o u t 2 2 0 0 lbs., free from moisture. Comparing t h e square foot cross-section of a cord of 2 feet a n d 4 feet woods, we observe t h a t t h e former averages a b o u t 50, or 7 8 per cent, while t h e latter
a n d balsam
YIELD I
T h e method of estimating total carbon i n soils by oxidation with a mixture of chromic a n d sulfuric acids has been tested b y different chemists with varying results, Warrington a n d Peakel found t h a t t h e chromic acid method gave lower results t h a n those obtained b y combustion in current of oxygen. Later, Cameron a n d Breazeale2 compared t h e chromic acid 1 1
Jour. Chem. Soc.. 37 (1880),617 Jour. A m . Ckem. Soc.. 26, 29.
562
T H E J O U R N A L O F I N D U S T R I A L A N D EiVGISEERILVG C H E X I S T R Y
combustion with dry ignition in combustion furnace; t h e lower results obtained with chromic acid combustion a s practiced by t h e m , were no doubt due t o t h e fact t h a t t h e mixture was heated only until t h e sulfuric acid began t o give off fumes. Hall and Miller1 reexamined t h e method a n d concluded t h a t t h e error was due t o incomplete oxidation, other substances t h a n carbon dioxide being produced. They found t h a t by passing t h e products of combustion over heated copper oxide, all t h e carbon could be obtained as carbon dioxide. Their method calls for t h e addition of concentrated sulfuric acid a n d heating before chromic acidisadded, whichmay account forthedifferences found. Soil investigations in progress required t h e determination of carbon in I per cent hydrochloric acid and 4 per cent ammonia extracts of soils. Since neither t h e combustion furnace nor P a r r apparatus2 could be used on account of impracticability of reducing volume of solution t o dry condition for combustion in boat or explosion bomb, t h e chromic acid combustion suggested itself as t h e most feasible method. This led t o a thorough test of t h e method for t o t a l carbon in soils, as compared with results obtained by combustion with copper oxide in furnace. T h e use of t h e Brown a n d Escombe double titration method for estimating carbonate in presence of sodium hydrate a s suggested b y Amos,3 a n d a modification of his apparatus has contributed much t o t h e successful operation of t h e chromic acid combustion as practiced in this work. T h e a p p a r a t u s as modified b y t h e junior author is shown i n cut with accompanying explanatory details. It can be assembled o n a single ring s t a n d a n d requires only 16 inches table space. T h e absorption t u b e permits of a much smaller volume of 4 per cent solution of sodium hydroxide for absorption of carbon dioxide, t h u s reducing t h e blank a n d making i t practicable t o t i t r a t e t h e entire solution instead of a n aliquot. B y adopting this procedure for determination of carbon dioxide rather t h a n t h a t of weighing a n absorption bulb, t h e long purifying train is eliminated. T h e only substance likely t o interfere with t h e titration would be hydrogen sulfide which could scarcely be evolved from such a strong oxidizing solution. This method was found t o be applicable for estimation of carbon dioxide evolved from either t h e wet or dry combustion. a n d was used throughout t h e work here reported. T h e soil samples selected for this work varied considerably as t o their formation a n d content of inorganic a n d organic carbon. DESCRIPTIONOF SOILS
Mineral carbon Litmus M a r r method reaction per cent Very acid 0.000 Pieutral 0.024 Very alk. 0.444 Acid 0.000 Neutral 0.000 ~~
Lab. N o . 4655,. . . . . . . . . . . . . . 4754.. . . . . . . . . . . . . . 4755,. . . . . . . . . . . . . . 5577-1.. . . . . . . . . . . . 1416-3. . . . . . . . . . . . .
Origin Swamp clay Limestone clay Limestone clay Silt loam Prairie TOTAL CARBON
T h e following methods were employed for estimation of total carbon in soil. J o u r . Chem. Soc.. 89 (1906), 595. Jour. A m . Chem. SOL.,2 6 , 296-1640. s Jour. Agr. Sci., 1, P a r t 3, 322. 1 2
I-IGiYITIOS
ITi
FURNACE
WITH
1-01. 6, N O , 7
COPPER
OXIDE-
F r o m I t o 3 grams of soil were thoroughly mixed in a n agate mortar with five times its weight of copper oxide, transferred t o porcelain boat a n d ignited in glass t u b e a t bright red heat for 30 minutes, a current of COZ free air passing through t u b e carrying products of combustion over heated copper oxide during t h e whole time. T h e gas was t u r n e d off a n d air allowed t o pass for I O minutes. The carbon dioxide produced was absorbed in 2 j cc. of 4 per cent sodium hydroxide made from sodium. When combustion was complete, t h e absorption solution was drawn out, t h e tower washed with I 50 cc. carbon dioxide-free distilled water a n d t h e solution t i t r a t e d b y double titration. using phenolphthalein and methyl orange. 2-C
0 11B US T I 0 N
W I T H C 0 S C E h-T R A T E D C H R 0 111C AS D
I t o 3 grams of soil were weighed into a 2 j o cc. short neck Kjeldahl nitrogen flask connected t o a p p a r a t u s ; I O cc. chromic acid solution containing 3.3 grams, then j o cc. of concent r a t e d sulfuric acid were run in through separatory funnel. This mixture was boiled 30 minutes, during which time a moderate current of carbon dioxidefree air was passed i n t o t h e boiling mixture, sweeping out t h e carbon dioxide evolved, which was absorbed a n d titrated as under copper oxide combustion.
SULFURIC
ACID BIIXTURE-From
COMBUSTION
WITH
DILUTE
CHROMIC A X D
SULFURIC
same as for concentrated chromic acid except t h a t j o cc. of water were added before t h e chromic a n d su'lfuric acids. S AT E3- C 0 h l B US T I 0 N W I T H A L K A L I S E P E R MA S G .i From I t o 3 grams of soil were placed in 2 j o cc. Kjeldah1 flask, I O O cc. of a solution containing 8 grams sodium hydroxide a n d j grams potassium permanganate a d d e d ; t h e flask connected t o t h e apparatus and boiled for one hour; t h e mixture was cooled, the 4 per cent solution of hydroxide placed in absorbing tower a n d j o cc. of one p a r t sulfuric acid a n d two parts water r u n into flask through separatory funnel. After boiling ~j minutes, t h e carbon dioxide evolved was determined by titration. ACID M I X T U R E - T h e
TABLEI-TOTAL CARBON-cOMP.4RISON
OF RESULTS B Y DIkFERENT
METHODS
1 2 Ignition Comin bustion furnace with with conc. copper chromic Lab. No. oxid acid 4.452 4655 4.446 3.600 4754 . . . . . . . 3.553 3.672 4755 3.654 1.152 5577-1 . . . . . 1.226 4.036 1416-3 . . _ . . 4.011
.......
3 Combustion with diluted chromic acid 4.152 3.324 3.430 1.068 3.792
5 Combustion with conc. chromic 4 acid passing over Differences Alkaheated in results line copper Column 1KMnOi method oxide Column 2 4.428 -0.006 3.780 3.552 -0.047 3.282 3.660 -0.018 3,180 1.156 0.074 1,063 4.044 -0.025 3.855
I t is seen from these results, t h a t for soils, t h e continued boiling with concentrated chromic acid gives results agreeing with those by t h e ignition method, within t h e limits of experimental error, while if t h e mixture is dilute, t h e results are too low, a n d t h a t t h e results obtained with alkaline permanganate are entirely t o o low throughout. T o determine if t h e oxidation with chromic acid had been carried t o a complete reaction giving carbon dioxide as t h e final product, t h e gases from combustion with concentrated chromic acid mixt u r e were passed over heated copper oxide before being
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I S E E R I N G C H E M I S T R Y
J u l y , 1914
absorbed. These results in Column j agree very closely with results obtained from combustion in furnace a n d with chromic acid mixture only (Columns I and 2 ) I n all cases where t h e digestion was made with t h e concentrated solution. t h e silicates of t h e soil were disintegrated a n d rendered gelatinous; upon dilution a n d filtering t h e digested residue, i t s bulk was found t o be greatly increased By rubbing in beaker with glass rod, very iittle grit was found t o remain. On reigniting three or four of t h e residues in 1 he furnace m-ith copper oxide. no carbon dioxide was recovered. This seems t o be conclusive proof t h a t t h e concentrated chromic a n d sulfuric acid treatment' completely decomposes organic a n d inorganic carbon present in soils a n d overcomes t h e objection raised b y Cameron a n d Breazeale, a n d Hall a n d hIiller in their articles previously cited. CARBOS I S
4 P E R C E N T A J I h l O N I b - 3 1 H Y D R O X I D E SOIL EXTRACT
T o determine whether or not moderate dilution prevented t h e complete oxidation of h u m u s materials b y this method, three duplicate j o cc. portions of t h e Grandeau h u m u s extract, equivalent t o I gram of soil, were pipetteti off; t w o sets were evaporated t o dryness on steam b a t h , a n d transferred t o t h e digestion flasks with three successive j cc. portions of 4 per cent ammonium hydroxide a n d 1 5 cc. of water. One of these sets was placed in water b a t h heated t o 65' C., a n d distilled t o dryness under reduced pressure, a n d carbon determined on t h e d r y residue. Carbon was determined on t h e other t w o sets without concentration. TABLE11-CARBON
I N HUMUSSOLUTION B Y CHROMIC ACID METHOD (Expressed as per cent of soil) On original In dry humus In humus solution residue after evaporated to dryness and not evaporated evaporating Lab. No. and distilling diluted to 30 cc. nor distilled 2.448 2.328 4655 . . . . . . . . . . . . . . 2 . 2 9 2 2.172 2.160 4754 . . . . . . . . . . . . . . 2 . 0 8 8 1.536 1.848 4 7 5 5 . . . . . . . . . . . . . . 1.620 0.696 0,672 5577-1 . . . . . . . . . . . . 0 . 7 2 0 2.316 2.712 1416-3.. . . . . . . . . . . 2 . 5 3 2
Average.. . . . . . . .
-
___
__
1.850
1.807
1.970
T h e results i n Columns I and 2 are within t h e limits of experimental error a n d show t h a t 30 cc. dilution does not prevent t h e oxidation of h u m u s substances. T h e difference between t h e averages of Columns I a n d 2 , a n d Column 3 can be accounted for b y t h e loss of \Tolatile a n d easily oxidizable carbonaceous m a t t e r through evaporation on t h e steam bath. I t is evident t h a t moderate dilution does not prevent t h e oxidation of humus b y chromic acid after i t has been extracted from t h e soil b y 4 per 'cent ammonium hydroxide. If all of t h e HC1 is not washed from t h e soil before extracting with 4 per cent ammonium hydroxide, a trace of C1 m a y come over a n d be absorbed. This m a y be corrected b y t h e addition of l / 2 cc. I O per cent sodium thiosulfate or by introduction of a U-tube containing silver sulfate between t h e digestion flask a n d absorption tower. 1 Adding the CrOa before adding H&O4 gives an oxidizing solution before the organic matter is charred b y H90,.
CARBON
IN
I
PER
CENT
563
HYDROCHLORIC
ACID
SOIL
EXTRACT
At first this determination presented some difficulties. All of t h e chlorine a n d chromium chloride were not condensed in t h e reflux condenser, b u t a portion was carried over a n d absorbed with t h e COZ. This destroyed t h e indicators. This defect was overcome by the addition of 4 cc. of a I O per cent solution of sodium thiosulfate just before titrating. This gave a clear, sharp end point with both indicators, a n d no further trouble was experienced in obtaining good duplicates. The volume of hydrochloric acid extract used was concentrated t o about 30 cc. b y distilling under reduced pressure before adding t h e chromic a n d sulfuric acids. I n order t o test t h e accuracy of t h e methods, a set of soils. j grams each, were extracted with I per cent HC1, then with 4 per cent ammonium hydroxide according t o official method of t h e A . 0. A. C., Bulletiiz 107,revised, Bureau of Chem., C.S. D. A. Instead of using Gooch crucibles with asbestos m a t , a n alundum crucible was used, eliminating t h e asbestos. T h e I per cent hydrochloric acid extract a n d washings were made t o a volume of j o o cc. Nine-tenths of t h e 4 per cent ammonium hydroxide solution was siphoned off, disturbing t h e settled soil as little as possible, leaving t h e residue from j grams of soil a n d one-tenth This of t h e 4 per cent ammonium hydroxide extract. was transferred t o beakers, evaporated, dried, ground in a n agate mortar a n d weighed. One-fifth of this was weighed into t h e digestion flasks, carbon determined, a n d results calculated t o per cent of carbon on basis of original soil, allowing for t h e carbon in t h e 4 per cent ammonium hydroxide. Carbon was determined on t h e I per cent HC1 a n d 4 per cent N H 4 0 H extracts, a n d t h e mineral carbon was determined b y t h e hfarr method.' T h e s u m of these fractions should equal t h e total carbon found in t h e soil.
.
TABLE1x1-COMPARISON
OF S U M OF FRACTIONAL DETERMINATION OF CARBONI N SOILSWITH THE TOTAL CARBON
*' O Y
I.
a2
*
L
a
- x
-
-E
8
2
4655.. . . . . . . . . 0.000 4 7 5 4 . . . . . . . . . . 0.026 4 7 5 5 . . . . . . . . . . 0.444 5577-1,. . . . . . . 0.000 1416-3,. . . . . . . 0 . 0 0 0
.f5
.-O
X
L
E 5 $;
E u 0 0.384 0.252 0.180 0.136 0.396
z
E 'a
e
2.532 2.220 1.860 0.600
2.568
1.391 4 , 3 0 7 1.110 3,608 1.194 3.678 0 . 4 5 6 1.192 1.051 4 . 0 1 5
A v . ,. . . . . . . . . . . . . . . . . . .
4.445 4 . 4 5 2 3.558 3.600 3.654 3.672 1.226 1.152 3 996 4 . 0 3 6
~ 3.320
3.375
-
3.382
I t is seen from these results t h a t t h e average differences between t h e total carbon determined direct, a n d t h e s u m of t h e fractions are well within t h e limits of experimental error, a n d t h a t t h e method as applied t o soil extracts is reliable a n d accurate. I n all t h e work here reported, every fifth determination was a blank made under exactly t h e same conditions as t h e determinations so t h a t t h e necessary correction could be made. OPERATION O F A P P A R A T U S
If i t is desired t o free t h e a p p a r a t u s from CO1 1
Jour. A g r . Sci., 3, Part 2, 155.
-
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 CHEMISTRY
564
before starting a determination, t h e arrangement shown a t Q m a y be inserted, glass “T” k k a t K a n d glass “T” 1 1 a t L , connected b y t u b e 0. By closing N a n d R a n d opening P, t h e COZ m a y be removed f r o m D , or b y connecting S with a tower similar to
at
L r
id
b
e-
Yol. 6, NO. 7
a n d liberate all carbon dioxide chemically or mechanically held in soils, provided t h e soil is ground t o pass 60 mesh sieve a n d from I t o 3 grams of soil used for each 60 cc. of mixture. If t h e mixture is diluted with jo cc. of water, t h e results obtained are t o o low. T h e alkaline permanganate method gives too low results. The Brown a n d Escombe titration method of determining carbon dioxide, a n d t h e modified Amos absorption tower for same, are applicable t o either wet or d r y combustion forms of apparatus, and can be relied upon t o give rapid a n d accurate results with considerable economy of time a n d space. Carbon m a y be accurately determined in I per cent hydrochloric acid extracts a n d 4 per cent ammonium hydroxide h u m u s solutions without concentrating below 50 cc. by using t h e above chromic a n d sulfuric acid mixture. T h e apparatus described is applicable t o t h e determination of carbon dioxide in a n y form, a n d a n u m ber of other gas determinations, depending on absorption in acid or alkalies, oxidation or reduction processes. By using t h e apparatus shown in t h e cut, a n d following t h e method as outlined, one analyst can r u n six determinations a t one time, a n d complete a set a n hour when doing routine work, making i t possible t o r u n forty-eight total carbons in a n eight-hour day. D E P A R T M E NOF T CHEMISTRY OHIO AGRICULTURAL EXPERIMENT STATION WOOSTER
~
A a n d leaving N a n d P open, closing R , t h e whole a p p a r a t u s m a y be freed from COZ. This is usually unnecessary since t h e blank takes care of t h e COa t h a t is in t h e apparatus. T h e sample is placed,in D which is connected t o C . . T h e absorbing liquid is placed in G a n d this connected t o tower T . T h e stopcock in B is closed a n d digesting liquid placed in B which is t h e n connected t o A . Water is started through condenser F a n d t h e suction started. R is slowly opened until t h e liquid in G is drawn into T a n d a moderate flow of air started. T h e stopcock i n B is opened a n d t h e digesting liquid r u n into D , using ordinary care. When air begins t o flow from A , t h e heat is applied t o D a n d t h e process continued t o completion. When this point is reached, remove flame, close R , disconnect B , t h e n G, a n d remove stopper from tower T . Receive content of T in G a n d wash o u t T with I O O cc. of COz-free water, using successive z j cc. portions a n d t i t r a t e content of G. T h e tower A a n d a p p a r a t u s T-G m a y be used for t h e determination of carbon by ignition in a furnace, without t h e use of t h e customary purifying train. This form of a p p a r a t u s is less expensive, more easily operated, a n d just as efficient as t h e one shown in THISJ O U R N A L , 4, 612. CONCLUSIONS
If boiled for 30 minutes, a mixture of 3.3 grams of chromic acid in I O cc. of water t o j o cc. of sulfuric acid (sp. gr. 1.84)will oxidize all of t h e organic carbon
_
_
THE MELTING AND SOLIDIFYING POINTS OF MIXTURES OF FATTY ACIDS AND THE USE OF THESE POINTS TO DETERMINE THE COMPOSITION OF SUCH MIXTURES By
E. TWITCHELL
Received March 25, 1914
T h e tables of melting points of mixtures of lauric, myristic, palmitic a n d stearic acids b y Heintz’ show certain regularities which Heintz himself noted, a n d which are referred t o by Ostwald i n his “Lehrbuch der Allgemeinen Chemie,” 2d Ed., Vol. I , p. 1017, where he observes t h a t it matters little which of these f a t t y acids of a lower melting point is added, in a certain proportion u p t o 40 per cent, t o one of a higher, t h e lowering of t h e melting point of t h e latter is almost t h e s a m e ; also a n y of t h e f a t t y acids of higher melting point m a y be added t o one of a lower (in definite proportion u p t o I j or 20 per cent) a n d will cause t h e same depression. I n other words, a n y of t h e f a t t y acids examined, when added i n a certain proportion up t o 2 0 per cent t o a n y other, wi’ll cause a lowering of t h e melting point of t h e solvent acid depending on t h e a m o u n t of t h e acid added b u t independent of its kind. This fact he explains b y t h e law of equal depression of t h e freezing point for equal molecular proportions. This explanation assumes t h a t t h e different f a t t y acids considered have t h e same molecular weights, which is, of course, not true, b u t t h e molecular weight of these f a t t y acids, a n d in fact of t h e f a t t y acids found in most 1
Poggendorff’s Annalen, 9’2, p. 588.
