A procedure is described for preparing barium titanyl oxalate tet rahydrate, BaTiO (Cz0 4h4 HzO, in which the mole ratio of TiOz to BaO is unity. To achi eve this ratio the alt must be precipitated from solutions that do not contain sodium, potassium, or ammonium ions.Ignition of barium titanyl oxalate tetrahydrate produces barium titanate, BaTi03• To prepare barium titanate free of strontium, the barium chloride used must be specially purified.

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From a study of cond itions under which certain base metals known to be associated with native grain platinum could be collectively separated from the plat inUIT\ metals and gold, a new procedure has been developed for analyzing dental gold 1o,,!10YS which differs cssentially from that published by W. H. Swa nger in 1926.The procedure as a pplied to dental gold alloys provides for the separ ation and gravimetric determination of silver, ~ridium, tin, gold, indium, copper, zinc, nickel, palladium, rhodium, and platinu m. Briefly it is as follows : Silver chloride and metallic iridium are precipitated when the alloy is decomposed by aqua regia. Tin is next separated by a new t echn ic of controlled h ydrolysis. Gold is then precipitated by sodium nitrite, and next, by adjusting thc alkalinity with sodium hydroxide to the end point of thymolphthalein, indium, copper, zinc, and nickel are coll ectively separated from rhodium and platinum. At this alkalinity a small proportion of palladium precipitates with the base metals but is recovered from them with dimethylglyoxime. Palladium, rhodium, and platinum are separated from one anoth r by the usual methods of this laboratory. The four base metals are separated, in order, by precipitating indium with ammonium hydroxide, copper, and subsequently zinc, with ,hydrogen sulfide, and nickel with dimethylglYoxime.It was found that manganese, iron, cobalt, and chromium are also quantitatively precipitated in a solution containing nitrite at the end point of thymolphthalein, and that it is possible to separate lead from palladium and platinum at the end point of xylenol blue, if the lead is precipitated as carbonate.Suggestions ate made for using the procedure as a refining method for crude material containing gold and the platinum m etals.

A method is described for the analytical separation of rhodium from iridium by means of titanous chloride. Two precipitations of the rhodium, as metal, from a solution of its sulphate in sulphuric acid were found to be sufficient to separate it completely from iridium. Following the separation, methods are described for the determination of rhodium by precipitation with hydrogen sulphide, for the elimination of titanium by precipitation with cupferron, and for the determination of iridium by hydrolytic precipitation.An alternative method is offered in which rhodium and iridium are determined together in one sample by hydrolytic precipitation, and rhodium separately in a second sample.

A m ethod is described fo r ~e]Jarat in g iod id e, b romid e, a nd chl o ride from one a not he r . First. th e iodid e ion is ox idi zed to eleme n tary iod ine b y h yd roge n p er oxide ill weak lv acid so lutio n a nd t he iodin e re mo ved b.v d istillat io n. Kext, bron Jide is oxidi zed to bro mine \~itho u t a fl.'c ct in g t he c hlorid e ion by use of a co nt roll ed con cen t rat ion of ni t ric a cid as ox id iz in g a ge n t . Af to r re mo va l o f bro llllll e b .v dlst dl a tlon , c hl o l'ld e re ma In s II1 t he reS Idu a l so lu t ion .D ete rmin a ti o n of th e indi v! du a l ha lid es depe nds on th e qu a n t ity of eac h. If in t race am oll n ts, a t lll'b id im et ri c m et hod is used; iF in larger a mo un ts, p otent io met l'l c t itr ation \\' ith s il ve r nit rat e is Ii sed.A d escript io n o f t he apparat us IIsed is a lso give n .