Oct., 1 9 1 1
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 N E E R I N G C H E M I S T R Y .
hydrochloric acid, barium sulphate was precipitated a s usual. 1. BaSOl found ( g n ~ ). .. . . . . . . . . . . . 0,5379 Sulphur (per c e n t . ) ,. . . . . . . . . . . . 3.69
.
2. 0,5395 3.71
3. 0.5437 3.73
4. 0.5417 3.72
The barium sulphate precipitates were then mixed with soda and potash and fused. The melts were dissolved in water, filtered a n d the residues washed with hot, very dilute sodium carbonate solution. The residues of barium carbonate and lead oxide were then dissolved in dilute nitric acid and the lead precipitated from the cold solutions b y hydrogen sulphide. After standing over night in stoppered flasks, the precipitates of lead sulphide were filtered off washed, dissolvgd in nitric acid and finally converted into sulphate b y evaporating down in porcelain crucibles with sulphuric acid and gently igniting. 1. PbSO, found (gm.).. . . . . . . . . . . . 0.0086 Equivalent t o BaSO, ( g m . ) . . . . . . 0.0066 Corrected BaSOl (grn.). . r . . . . . . . 0.5359 Corrected sulphur (per cent.). . . . 3.68
2. 0.0071 0.0055 0.5379 3.69
3. 0.0040 0.0031 0.5428 3.73
4.
0.0045 0.0035 0.5407 3.71
It is quite evident from these figures t h a t although notable quantities of lead sulphate are carried down with the barium sulphate, the correction in the percentage of sulphur is negligible. The filtrates from the original precipitates were treated with hydrogen sulphide and gave slight precipitates. The alkaline filtrates from the barium carbonate and lead oxide were tested with ammonium sulphide and became brown. The next day there was a slight film of a dark color on the bottom of each of the beakers in which these solutions were tested. This was probably a mixture of small amounts of lead and iron sulphides. I n all the solutions tested, as well as in the actual determinations of lead sulphate, greater amounts of lead were found in I and 2 , which had been treated with bicarbonate. Apparently at the temperature of the steam-bath the lead bicarbonate probably formed was not decomposed. CONCLUSIOXS.
Treatment of the rubber with nitric acid alone gives low results (compare XV with X V I I I ) . This is probably largely due t o loss of free sulphur, since nitric acid alone does not completely oxidize sulphur t o sulphuric acid in the length of time ordinarily taken for a determination. The Hubener met,hod cannot be employed in the presence of mineral fillers which tend t o form insoluble sulphates. This applies especially to barium carbonate and litharge. A comparison of X X t o X X V I I shows that the fusion method gives results very close to those obtained b y direct precipitation and b y neutralization. The van't Kruys method gives high results. The best results seem t o be obtained b y the use of method XVIII, according to which the rubber is decomposed b y means of nitric acid saturated with bromine. BUREAUOF STANDARDS, August, 1911.
737
CONSISTENCY OF PAINTS BY THE STORNER VISCOSIMETER. B y ALLEXROGERSAND A. H SABIN.
Received June 9, 1911.
Those who have ever attempted to take the viscosity of a paint will appreciate that it is no easy matter. At a meeting in Atlantic City, last June, i t was suggested b y Mr. P. H. Walker and Prof. A. H. Sabin that the Stormer viscosimeter might be used for this purpose, especially the apparatus, as modified, a t the suggestion of M r . C. N . Forrest, from the paddle t o the cylinder type. I t was the writers' desire t o obtain some method for checking the exact consistency of a large number of paints, and do it in such a manner that the personal factor would be eliminated. A sample of paint was, therefore, prepared which, in the writers' judgment, was of the proper consistency for application. The viscosimeter was adjusted with this paint so t h a t the dial made a complete revolution in two minutes. A sample of paint made b y the Patton Paint Co. came very close t o the paint made b y the writer, as well as one made by the Sherwin-Williams Co. To get a more definite standard, however, 95 per cent. glycerine was tested and, strange t o relate, the dial made a complete revolution in exactly two minutes. Therefore, glycerine, a t 2 o o C . , was taken as the standard, and all subsequent tests made a t this temperature.. During the past two months several hundred viscosities have been taken, and although the machine has been tested each morning before the day's work it has not been found necessary to readjust the weights. The apparatus, however, requires quite a bit of attention and should be frequently cleaned and oiled. I t is very essential also t o have the temperature exact, as one degree will make quite a difference in the reading. The viscosimeter consists of a flat-bottomed cylindrical cup I'/* inches internal diameter b y z T / Z inches deep having two radial vertical wings or septa I/, inch wide attached t o its inner wall, and extending from the bottom t o within inch of the top, being in fact obstructions t o the rotary flow of the liquid. Within this cup is suspended a stirrer, the revolution of which is resisted b y the viscosity of the liquid; this stirrer is a hollow metal cylinder 13/, inches long and I I / ~inches in diameter, its lower end open, the upper end closed except it contains four holes, each inch in diameter, symmetrically arranged. This cylinder is supported from above by a vertical rod or shaft, concentric with the cylinder but external to i t , being 3 / 1 6 inch in diameter by z l / ( inches long. The end of this is attached b y a collar and screw t o the bottom of a vertical shaft which carries a pinion 1/2 inch in diameter, having 2 5 teeth, which in turn is driven by a gear 5 1 / ~inches in diameter with 2 7 j teeth, t o which large gear is attached a drum I I / ~ inches in diameter, around which is w o m d a small silk cord, the external portion of which passes over a small pulley and is attached t o a driving weight. The top of the shaft carrying the small gear carries ,also a screw or worm which engages and drives the
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 N E E R I N G C H E M I S T R Y .
738
serrated edge of a graduated disk or dial, one revolutiqn of which marks I O O revolutions of the stirrer. The stirrer is suspended so t h a t its bottom is ’//, inch above the bottom of the cup, and in consequence its top is ”/, inch below the top of the same; when in use the cup is filled t o within ”/, inch of its top inch above with liquid which, therefore, stands ”/, the top of the stirrer. To make a hundred revolutions of the stirrer the weight descends about 39 inches. The stirrer comes within inch of each side of the radial wings, one on each side of the cup, already mentioned. The index of viscosity may be defined as the force required t o produce a given shear in a given time; if we adopt a minute as the unit of time, and the shear produced b y I O O revolutions of the stirrer as the unit shear, the viscosity will be indicated by the ?umber of grams (units of weight) required t o cause the stirrer to revolve roo times in one minute. Allowance should be made for the friction of the machine, which in this instrument is about 5 grams. It has a friction clutch which, being opened, allows it to start ; it is used with a stop-watch. As a t present sold it is not provided with a suitable scale-pan and weights, but is supposed t o be used with a fixed weight, which is sufficient if we wish only t o bring various mixtures to one standard, but is like using a fixed measure instead of a scale. I t is very important t o use i t a t a standard temperature, LABORATORY OF INDUSTRIAL CHEMISTRY, PRATT INSTITUTE, BROOKLYN.
A STUDY OF CARBON IN SEWAGE AND SEWAGE PURIFICATION. By H W CLARKAND GEORGE0 ADAXS
Received June. 1 1911
1
The part that nitrogen plays in sewage a n d sewage purification and in the analysis of sewage and water is well known t o all engaged in sanitary work that has t o do with water and sewage or their purification. The important part played by carbon and carbonaceous matter is, however, not so well understood; neither is the relation t h a t carbon bears to nitrogen in the composition of sewage and water, in analytical work and in sewage purification, fully comprehended. Carbon, however, is the chief constituent of the organic matter in sewage and is a troublesome factor in the satisfactory disposal of sewage. I t is carbonaceous matter, moreover,Jhat gives color and other objectionable characteristics to some water supplies. To such sanitary chemists and engineers as construct, operate or study sewage plants, sewage filters, etc., the problem of carbon disposal appears more and more important. This is especially true when industrial sewage is t o be treated. For a more complete understanding of that portion of the problem of sewage purification t h a t has t o do with carbon, studies have been made a t the Lawrence Experiment Station fr& time to time during the past ten years in regard t o the amount of carbon in sewage and water; the relation t h a t carbon in samples undergoing analysis bears t o the results of loss on ignition and oxygen 1
Laurence Experiment Stabon, Mass State Board of Health
Oct.,
1911
consumed determinations and t o other bodies t h a t may be determined by the analysis of sewage and water, and of the work accomplished b y various classes of sewage filters in caring for the purely carbonacepus bodies in the sewage applied t o them. I n various reports of the Experiment Station during the past seven or eight years, much data accumulated in these studies have been given. I n this work as elaborated in the reports, many comparisons have been made between the amount of nitrogen and carbon in the samples analyzed and the relative amount of oxygen necessary t o oxidize the‘ carbon compounds as compared with the amount necessary to oxidize the nitrogenous bodies in sewage. The following paper presenting a summary of much of this carbon work, together with the results of additional studies, can be properly divided into several sections. Between some of these sections there may not seem to be any very clearly defined relation, but all have t o do with carbon, nitrogen and oxygen in searage and its purification. ( I ) KO. I deals with the determinations of the actual amount of carbon in samples of sewage and water and gives a comparison of the amount of this carbon with the amount of organic and other matter determined by the loss on ignition process; ( 2 ) No. z is in regard to relative amounts of carbon and nitrogen in sewage; (3) Yo. 3 deals with the relaticn between carbon and fatty matters in sewages; (4) S o . 4 compares the per cent. t h a t carbon forms of the loss on ignition determinations when sands from sewage filters that have been in operation are examined; ( 5 ) No. 5 gives the results of a series of studies of the oxygen consumed process, so-called, and what i t shows in regard to carbonaceous and nitrogenous matter in water and sewage; (6) No. 6 treats of the relation between the amount of each oxidized or stored in suck filters; and ( 7 ) 7 treats of the influence of carbon on nitrification. CHAPTER
NO.
1.-COMPARISON
OF
CARBOX A K D
LOSS
O N IGXITION.
I n order t o determine and show the amount of carbon in average samples of sewage and water and the relation between carbon and loss on ignition, dry residues from the evaporation of forty-four samples of seyages, waters, etc., were obtained. These samples were as follows: Twelve samples of sewage and ten of the same samples after filtration through paper, nine samples of surface waters, three of well waters, five effluents from sand filters which had received sewage for many years, three effluents from trickling sewage filters operating a t a high rate and two mill wastes, both unfiltered and filtered through paper. I n obtaining these dry residues for analysis, the following precautions were taken: First, dust was carefully excluded during evaporation ; second, the alkalinity of each sample was neutralized t o avoid error in the final results due t o the decomposition of carbonates during the combustion for the determinations of carbon, and a n allowance was made for the decrease in weight of the residue due t o neutralizing the carbonates. Carbon combustions were made b y
I
