AW.9 1914
T H E J O I:R N A L O F I N D 17s T R I A L A ATD E N G I N E E RI N G C H E M I S T R Y
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1
a-The a m o u n t of water retained when a n ordinary filter is used varies from 11 per cent, with 2 0 mesh material, t o 20 per cent with I O O mesh material, one hour being allowed for drainage. 3-The a m o u n t of water retained on a filter with z in. vacuum averages 7 per cent after I j minutes for material varying from 30 t o 80 mesh. 4-111 a layer of material 7 0 cm. deep on a filter, with j in. v a c u u m , t h e t o p layer will average, after I j minutes, 4 per cent moisture, a n d t h e b o t t o m 6.5 per c e n t ; t h e size of t h e grains is n o t of importance within t h e limits discussed. ' If t h e vacuum be maintained for 15 minutes longer, t h e above figures will be reduced b y another half per cent. j-By t h e use of a centrifugal, t h e percentage of moisture, i n all t h e materials employed, m a y be reduced t o a n average of 2 . 5 per cent. 6-In t h e case of a s a n d of 30 mesh with 6 per cent moisture, if all t h e water be distributed over t h e surface of t h e particles, each grain would h a v e a film 0.0116 mm. t h i c k ; or t h e water would fill 30 per cent of t h e pore space. FACULTY OF
factory. Incidentally, i t m a y be s t a t e d t h a t all eft'qrts t o get t h e hard rubber people t o provide a material which would s t a n d u p against cold concentrated sulfuric acid have been futile. Hence, i t m a y be well t o warn others as t o their claims in this respect. A pear-shaped screen of copper gauze was placed in t h e opening of Tower B leading t o Tower A t o prevent clogging, in t h e event a rushing action of t h e p u m p sucked pieces of t h e pumice. We draw off a n d replenish t h e acid once or twice a year. Tower A is half filled with angular pieces of commercial caustic soda, in size from a hazel n u t t o a n egg. T h e mass rests upon a copper wire gauze screen
APPLIED SCIENCE
UNIVERSITY OF TORONTO TORONTO, CAXAIIA
SCRUBBER FOR CHEMICAL LABORATORY VACUUM SYSTEM' BY CHARLESBASKERVILLE
I n order t o protect t h e vacuum p u m p of our laborat o r y from t h e corrosive action of t h e gases drawn therein, I devised t h e installation described herewith. T h e pump-an improved Packard Vacuum P u m p , 2 cylinder, I a in. diam., motor-belt driven-has been in more or less continuous service for seven years without a n y expenditure thereon for repairs, as a result of this protection. It seemed safe, therefore, t o present a n account of it. T h e installation is a n application of t h e simple principles usually applied o n a small scale with glass a p p a r a t u s in t h e laboratory. T h e towers are made of cast iron, porcelain-lined, a n d set into t h e system with a by-pass, which we have used only during t h e short time necessary for recharging. T h e towers are connected b y hard rubber pipes ( a in. internal diameter). A t t h e b o t t o m of each tower is a h a r d rubber drain cock, bolted t o a flange. At t h e t o p of B a n d C are plates bolted t o flanges, which m a y easily be removed. T h e opening is of sufficient size t o a d m i t dropping a s t r u n g incandescent bulb for inspection. Tower B is three-quarters filled with pumice stone in egg-size pieces. T h e pumice is thoroughly saturated with concentrated sulfuric acid. I believe lead pipe would be better in this cylinder as t h e h a r d rubber softened on contact with t h e acid. So far, however, t h e weight of t h e pumice a n d acid has not been sufficient t o cause t h e h a r d rubber pipe t o collapse. T h e decomposition of t h e rubber compound became so pronounced with t h e drain cock in a short while t h a t i t was replaced b y a lead plate, which has proven satisPresented at the 6 t h Semi-annual Meeting of the American Institute of Chemical Engineers. T r o y , X e w York. June 17-20, 1914.
SCRUBBER FOR CHEMICAL
A-Caustic
LABORATORY VACUUM
Soda, B-Sulfuric
SYSTEM-SCALE,
1
IN. =2
FT.
Acid and Pumice; C-Trap
supported on a n d b y t h e tapering bottom of t h e tower. T h e drain cock admits of drawing off a n y liquefied caustic which m a y accumulate. A metal pipe leads from t h e t o p t o t h e pump. Tower C is a safety reservoir t o catch t h e fluid f r o m B i n t h e event of a leak beyond or other cause for increase in pressure on t h e p u m p side in t h e line. So far, no indication of its real need has been apparent, as t h e maximum a n d minimum contacts of t h e automatic regulator of t h e motor have never failed. A gauge in t h e system beyond t h e scrubber serves, by comparison with t h e gauge on t h e p u m p , t o show leaks i n t h e scrubber. Xone was observed until t h e h a r d rubber drain cock on Tower B failed, a n d none
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 C H E M I S T R Y
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has been noted since t h e change described above, over six years ago. T h e whole installation is supported on angle iron, painted with a rust-proof paint a n d may be inspected b y members of t h e I n s t i t u t e a n y time. COLLEGE OF
THE
CITYOF NEWYORK
NEW APPARATUS FOR DETERMINATION OF HYDROGEN SULFIDE IN WATER-PART I By GEO. B. FRANKFORTER
Received May 18, 1914
Hydrogen sulfide has been known with absolute certainty since t h e 15th century. It was first recognized i n natural water under t h e name “sulfur vapors” a n d t h e water was known as “sulfur water.” It was known t o Paracelsus who studied sulfur carefully a n d used it extensively in his medical work. He must have known of its presence in certain natural waters. Scheele, however, was t h e first t o give exact knowledge concerning its properties. He designated i t a s a.compound of sulfur, phlogiston a n d heat, a n d made a n effort t o determine t h e a m o u n t of sulfur in t h e gas. Since Bertholet’sl classical work o n its composition m a n y methods have been employed for its quantitative determination. I n general t h e methods of analysis are grouped. into t w o classeg, gravimetric a n d volumetric. The first exact method for its determination was given by Bunsen,2 in which he used iodine. Bunsen recognized some of t h e difficulties in t h e method, for he states t h a t t h e q u a n t i t y of iodine used must be small for good results. He also noticed for t h e first time t h a t hydrogen sulfide decomposes very readily so t h a t t h e estimation is often not very exact. Since Bunsen’s timc t h e iodine or iodometric method has been modified so as t o meet t h e different conditions under which t h e gas occurs. For instance, special a p p a r a t u s a n d special modifications in t h e iodine method are necessary for its determination in illuminating gas, a n d special a p p a r a t u s is necessary or a t least highly desirable for its rapid determination in n a t u r a l water as it decomposes when exposed t o t h e air a n d light. M y attention was called t o t h e fact t h a t water from a sulfur spring, after it had stood for a d a y or so in a clear glass bottle-whether directly exposed t o air a n d light or not-showed b u t a trace of gas, although i t was present in t h e water in appreciable quantities when t h e sample was taken. I was aware t h a t t h e gas, when dissolved in water containing air, readily decomposes liberating free sulfur, b u t I could hardly believe t h a t t h e sulfur water hermetically sealed would change very rapidly if t h e water contained dissolved air. I n t h e case of a spring water containing approximately I cc. per liter, t h e gas was entirely dissociated in six hours after t h e sample h a d been taken from t h e spring. . So rapid was t h e dissociation in this particular spring t h a t i t was quite impossible t o obtain concordant results without making t h e analysis right a t t h e spring. 1 1
A n n . ckim.. 1791. Ann. Chem. Pharn.. 86, 265.
Vol. 6 , N o . 8
I n order t o do this, however, i t was found necessary t o carry considerable a p p a r a t u s along, making t h e whole method quite unsatisfactory. I therefore experimented with a number of different forms of apparatus which could be carried around without difficulty, a n d which would simplify t h e process in such a way t h a t it might be used for field service. After trying o u t a number of forms t h e two following were found t o give perfectly satisfactory results. Figure I consists of a flask, “A”, which holds exactly joo cc. of water when filled t o “G”. “ C ” is a b u r e t t e with a stopper, “D,” connected with flask “ A ” by means of a three-way cock, “B”. “F” is a funnel t u b e also connected with “A” by means of a three-way cock
“E”. Manipulation is as follows: T h e three-way cock “E” is t u r n e d so t h a t t h e opening in t h e e n d of t h e cock is directly connected with “ A , ” (‘B” is likewise
fff.
z
turned so t h a t t h e opening in t h e end of t h e cock is connected with “ A . ” T h e flask is t h e n t h r u s t into t h e water t o be examined. Water enters “E” forcing t h e air out through “ B ” until t h e flask is full. On removing t h e flask, “ E ” acts a s a siphon allowing t h e water t o run out t o t h e level “G.” By this means exactly 500 cc. of water can be measured. Cock “E” is now turned a quarter way around, connecting funnel “F” with “ 4 . ” One cc. of starch solution is introduced, “ E ” is closed a n d t h e water is t i t r a t e d with s t a n d a r d iodine solution f r o m burette “C.” From t h e a m o u n t of iodine solution used t h e q u a n t i t y of hydrogen sulfide may be calculated according t o t h e following equation: HZS I p = 2 HI S I n rapid work, a n d especially in field work, it is very
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