264
T H E JOURNAL OF I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y .
ducing a new pattern in double cone ball-mills which permitted of the introduction of water and washing out of the charge without stopping the mill. The body of the mill was of the familiar type employed in horizontal mills, but the outlet was made considerably wider than the charging hole so that when the level of water within the mill was raised i t would overflow a t the outlet only. This proved of the greatest convenience and value in operating. After conversion was completed a jet of water was turned into the charging hole and the rotation of the mill continued. The hydrate in the form of an impalpable sludge was, of course, kept continually stirred up and was rapidly floated through the outlet into a washing vat. This water-floating action had the additional advantage that by no possibility could any portion of the charge escape from the mill before it was reduced to extreme fineness. Washing was effected b y decantation and the hydrate was then ready for conversion into other compounds. For conversion into chromate i t was dropped from the washing vat into a large percipitating vat and treated with the theoretical amount of acetic or nitric acid required for its conversion into a basic salt; water was added and the necessary solution of an alkaline chromate or bichromate. The extreme reactivity of the hydrate enabled the conversion to be effected without heating and with no more than the theoretical amount of acid. For the production of oxides the hydrate was pumped into a filter press and the cakes furnaced without previous drying. I t was found possible t o produce a good lead arsenate a t a considerably lower cost than obtains with present processes by mixing the freshly made hydrate with a solution of arsenic acid obtained by oxidation of arsenious anhydride with nitric acid, and boiling. The reaction was a little slow but the product most satisfactory. Other instances of easily obtainable compounds might be cited but the possibilities of lead hydrate are manifest. While the method offers absolutely nothing new from a chemical standpoint, it promises to have a very considerable influence upon the lead pigment business on account of the great economy over present methods which it entails. The degree of saving effected by using a by-product such as “blue fume” and thus saving both the smelting cost of producing pig lead and the additional cost of furnacing the pig lead to litharge and pulverizing the litharge is apparent from the following tables : The cost of producing chrome by present methods varies somewhat according to the market rates for litharge, acetic acid, nitric acid and sodium bichromate; the following figures represent usual costs in manufacturing on a large scale: Cost per cwt. 69 pounds litharge a t 5 % c . . .. $ 3 . i 9 . . 1.38 43 34 pounds 56y0 acetic ac 2.53 46 pounds sodium bichromate a t 5 % c . . Labor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 0.05 Water and fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packages and packing. . . . . . . . . . . . . . . . . . . . . . . . 0.25
........
$8.25
April,
1912
To this must be added freight and selling expense. These figures are based on good practice without waste. Most manufacturers compute their cost of production a t from $8.50-$8.75. For small producers who have to buy in small lots and a t higher prices the cost is*much higher. COST
OF
PRODUCING
CHROME
UNDER
NEW
PROCESS.
Using the same basis of prices as before. the cost per cwt. is:
.................. ............. ........... ........
11 pounds caustic soda a t 2 c. 80 pounds burned fume a t 2 % c . . 29 pounds 56% acetic acid a t 3 34 c . . 46 pounds sodium bichromate a t 5 34 c.. Labor ...................................... Water and fuel. ............................ Packages and packing.
.......................
$0.22 2 .OO 1.38 2.53 0.25 0 .OS 0.25
$6.68
To this must be added freight and selling expense. It will be observed that less acid is used than in the former statement. This is because of the much greater reactivity of lead hydrate as compared with litharge. The burned fume is valueless except as a smelting material: its value is therefore the value of the metal which can be recovered from it, less the smelting cost and freight.
A METHOD FOR TESTING OUT PROBLEMS I N ACID PHOSPHATE MANUFACTURE.’ By F. B. PORTER. Received Jan. 12, 1912.
The process of manufacturing acid phosphate is, like many other factory processes, very hard to carry out on a laboratory scale. The writer has a t vaqious times made attempts to do this on 1000 or more grams of rock dust. It has so far been practically impossible to stir sufficimtly and control the temperature well enough with the limited apparatus available to get satisfactory results. This being the case we recently devised the plan of using the quantities of acid and rock required t o make 2 grams of finished acid phosphate, stirring them together with a stirring rod in a test tube and using the entire product for the insoluble test. The following is the method in detail: Weigh 1.100grams of rock dust into a 5” X . 5 / / test tube, add the quantity of acid required from a small bore I cc. Mohr’s pipette, allowing the pipette to run empty and draining for a definite length of time ( I minute). The acid required and used is determined by titrating amounts delivered in the same way with halfnormal alkali. Stir the acid and rock together for 3 minutes, being careful to see that the dust is all wetted by the acid in the first half-minute of the stirring period. The test tubes thus prepared, without removing the stirPresented a t the forty-fifth meeting, American Chemical Society, XVashington. December. 1911.
April, 1912
T € € E J@L-RS,-ILOF IiVDGSTRI;1L
ring rod, are then held a t any temperature for any time desired. The resulting acid phosphate is transferred to a 9 cm. filter paper with water and the citrate-insoluble phosphoric acid determined by the Official Method. Page 3, Bull. 107,Rev. Bureau of Chem. At first this method gave occasional erratic results b u t with practice and care we are now able to get results agreeing practically within the limit of error of the citrate-insoluble method. The results used in this kind of work are averages of three and in most cases four separate analyses. I n this r a y accurate reliable results are obtained This method has many advantages over one using larger quantities of rock. Three of these are: 1st. Large numbers of tests can be carried out with inexpensive apparatus common to every laboratory. 2nd. The temperature at which the tests are held can be easily and accurately controlled. 3rd. A large number of these tests can be made in the time required for one by any other method known to the writer.
There was available a considerable quantity of each of the two samples for the 1909 A. 0.A. C. soil work, and as the average of results from a large number of independent workers is likely to be somewhere near the truth, it was thought that here was an unusually good opportunity to compare the two methods. Four determinations were accordingly made on each of the two soils, under conditions parallel to those used by the A. 0. A. C. workers, and the results are presented in Table I , accompanied b y the Association results on the same. TABLEI. so11 I . ICnorr method. .4nalyst. 3.
2.
1.
4.
0.070
0.085
0.072
0.073 0.065 0.072
0.082
0.073
0.068
...
0.073
...
-__ Av. 0 . 0 7 0
.
,
, .
.
0.083
. . . . . .
1.
0.027 0.028
Up to a comparatively recent time no method had been so thoroughly tried out as to be considered a reliable one for small amounts of carbon dioxide in soils. In 1908, the Association of Official Agricultural Chemists took up the matter of testing the applicability of the Knorr method, and in 1909 a still larger amount of cooperative work was done. The results of the work will presently be presented in tabular form . The method outlined in the author's previous paper1 having been found to yield good results with materials containing a large percentage of carbon dioxide, i t remained t o be seen whether i t would be as satisfactory in cases where the percentage is small. As a preliminary, two determinations were made in a sort of artificial soil containing a known amount of carbon dioxide. A very pure sea sand was ignited for some time to remove all organic matter and decompose such calcium carbonate as might be present from finely divided particles of sea shells and other carbonate materials. This was cooled, and to a v-eighed portion was added enough analy7ed CaCO, to give exactly 0.05 per cent. CO,. A blank determination was first made on the water, reagents, and freshly ignited sand; then two determinations were carried out on the artificial soil. The blank first found was deducted from the titration results, and CO, calculated from the difference. The determinations gave 0.043 and 0.048 per cent. CO,, a n average of 0.0455 as against the 0.05 per cent. actually present, which seemed very satisfactory. THISJOURNAL, 4 , 203-205 (March, 1912).
0 085 0.082
6.
_
_
~
_
7.
0.080
0.074
0.074 0.080
0.080
0.080 0.077
...
0.075
0.080
... ...
0,084
...
... ...
0.077
0,079
. . . . . . 0 085 . . . . . . . . . . . . . . . _
-
0 . 0 7 3 0.092 0.086 0 . 0 7 9 General av. 0.078
2.
3.
0.027 0 . 0 2 3 0.035 0.021
0.031 0 . 0 2 8 0.024 0.035 0.02; ...
ON THE DETERMINATION OF CARBON DIOXIDE I N SOILS.
.
0.092 0.085
-
Soil 2. Analyst.
ATLANTA,Gh.
B y LEON T. BOTSSER
.. ... ,
0.075
LABORATORY, SWIFT FERTILIZER WORKS,
Received October 26, 1911.
5.
0.092
Volumetric method.
0.023
0.020 0.022
4.
5.
6.
7.
0.027
0.027 0.027 0.030
0.036 0.036
0.026 0.025
0.030
...
.... ...
. . . . . . . . . . . . .
- ~ _ _ _ _ _ _ _ _ .Iv. 0 . 0 2 7
0 , 0 3 1 0 . 0 2 2 0 . 0 2 7 0 . 0 2 8 0.034 General av. 0.028 Comparison of Averages. Soil 1. A. 0. A. C.. \-olumetric.
. . . . . . . . .0 , 0 7 8
. . . . . . . . . 0 . Oi9
... ...
__ 0.025
0.026 0.031 0.031 0.026
...
0.028
Soil 2. 0 028 0.028
The averages given in the Association report are: I , 0.081 per cent.; No. 2 , 0 . 0 2 7 per cent. CO,, b u t these include only the results of the first five analysts, the latter two reporting too late to be included. For the present work all of the results are considered, increasing the probability that the averages are near the truth. The agreement between these revised averages and the ones obtained by the volumetric method is remarkably close, and shows that the latter is thoroughly reliable. On the score of consistent results, the volumetric method is superior to the gravimetric. Thus on Soil I the A. 0.A. C. results range from 0.065 to 0.092,a variation of 0 . 0 2 7 per cent., while the volumetric results range from 0.075 to 0.084,a variation of 0.009 per cent., or just one-third of the former. On Soil 2 , the A. 0. A. C. results run from 0 . 0 2 0 to 0.036, a variation of 0.016 per cent., as against 0.026 to 0.031, a variation of 0 . 0 0 5 per cent. for the volumetric, which, as with Soil I , is practically one-third as great a difference. The method followed was as outlined in the preceding paper,' and in each case I O grams of soil were taken. Soils containing 0.1 per cent. or less of CO, require for titration an acid of strength not exceeding hT/So, since when stronger acids are used the evolved CO, is equivalent to but a fraction of one cc., and too
No.
1
THISJOURNAL, 4, 203.
