Shaking apparatus for keeping

Selenium(IV) oxychloride, 3 130 Selenium (II) xanthates, 4 91 Selenocyanates, metal, 2 186, 188 Shaking apparatus, for keeping... 

IsoValeric acid. Prepare dilute sulphuric acid by adding 140 ml. of concentrated sulphuric acid cautiously and with stirring to 85 ml. of water cool and add 80 g. (99 ml.) of redistilled woamyl alcohol. Place a solution of 200 g. of crystallised sodium dicliromate in 400 ml. of water in a 1-litre (or 1-5 litre) round-bottomed flask and attach an efficient reflux condenser. Add the sulphuric acid solution of the isoamyl alcohol in amaU portions through the top of the condenser shake the apparatus vigorously after each addition. No heating is required as the heat of the reaction will suffice to keep the mixture hot. It is important to shake the flask well immediately after each addition and not to add a further portion of alcohol until the previous one has reacted if the reaction should become violent, immerse the flask momentarily in ice water. The addition occupies 2-2-5 hours. When all the isoamyl alcohol has been introduced, reflux the mixture gently for 30 minutes, and then allow to cool. Arrange the flask for distillation (compare Fig. II, 13, 3, but with the thermometer omitted) and collect about 350 ml. of distillate. The latter consists of a mixture of water, isovaleric acid and isoamyl isovalerate. Add 30 g. of potassium not sodium) hydroxide pellets to the distillate and shake until dissolved. Transfer to a separatory funnel and remove the upper layer of ester (16 g.). Treat the aqueous layer contained in a beaker with 30 ml. of dilute sulphuric acid (1 1 by volume) and extract the liberated isovaleric acid with two... 

Place 100 ml. of the SnClj-HPOj filtrate in a large test tulie. Introduce into the filtrate a gas filter tube with a sintered glass filter, about 20 mm. in diameter connect the test tube to a HjS tank and pass HjS slowly through the solution for 15 minutes. The test tube should be fitted with a rubber stopper throi h which are passed the HjS tube and an exhaust tube, which in turn is passed into a laige flask containing lime water to absorb the H2S the entire apparatus is placed under a hood. To 50 ml. of the HjS-saturated solution add 0.5 g. of thiourea, shake until dissolved, and filter. Bubble CO2 through the filtrate for 5 minutes. Pipet 4 ml. aliquots of this solution into each of three matched colorimeter tubes. Add 1 ml. of 2% 2,4-dinitrophenylhydrazine in 9 AT H2SO< to two of the tubes and keep one tube as a blank. Place the three tubes in a water bath at 37 C. for 6 hours. From here on the analysis is the same as that described above for the Norit filtrate. The result obtained here is the DKA value. 

---