CHEMICAL SCIENCE. 225 



the most effective tests we possess. The formula of its preparation 

 is as follows : Take of pure white starch 1 ounce, iodide of potassium 

 3 drachms ; mix in a marble mortar, and add gradually 6 ounces of 

 boiling Avater. The papers to be saturated with the mixture while 

 hot, carefully dried out of contact with the external air, and preserved 

 in close tin boxes." Mr. Lowe remarks: "Assuming that we have 

 adopted the best tests and the most approved method of using those 

 tests, it will be requisite to correct the readings for the velocity of 

 air at the time, for the hight of the barometer, for temperature, and 

 for the hygrometrical condition of the atmosphere. It must be borne 

 in mind that if in a given time 1,000 cubic feet of air passing through 

 the ozone-box gives a register of four, 2,000 feet passing through in the 

 same time will give one of double that amount. Moisture can also in- 

 crease or diminish the action, a very dry air or a perfectly saturated at- 

 mosphere showing a minimum. The lower the barometer descends, the 

 more ozone is shown upon the tests. In very hot or very cold weath- 

 er ozone is also at a minimum. With a west there is much more 

 ozone than with an east wind. The maximum amount of ozone will 

 occur with a moderately moist atmosphere, a temperature between 50 

 and 60, a barometrical pressure under 29 inches, and a gale occurring 

 at the same time. Before the actual amount of ozone can be ascer- 

 tained, certain corrections must be applied, and until uniformity is 

 adopted the observations cannot be made comparable. Under these 

 circumstances, we can do little more than record much or little ozone. 

 1} n't i till j\lcd. Journal, Oct. 1864. 



New Source of Ozone. Cosmos mentions a process of M. Boelger 

 for obtaining a continuous supply of ozone. He mixes two parts by 

 weight of finely-powdered permanganate of potash with three of sul- 

 phuric acid. A mixture of one part of the permanganate w r ith that 

 of the acid, is so powerful an oxydizer as to produce inflammation 

 and explosion if brought into contact with essential oils. 



THE COMPRESSION OF GASES. 



An accident, through the breaking of apparatus, was reported 

 recently by Dr. Frankland to the London Chemical Society. Being 

 desirous of using oxygen gas under great pressure in the laboratory 

 of the Royal Institution, he procured the apparatus made for the pur- 

 pose by Natterer, of Vienna. During its use an accident occurred 

 which fortunately led to no serious results, but which, he thought, 

 merited the attention of chemists. We extract from the Chemical 

 Gci-:elte the following particulars given by the Professor : The appa- 

 ratus consisted of two parts. On the one hand, a powerful compres- 

 sion-pump, worked by a crank and flywheel, which forced the oxygen 

 or other gas into a strong cast-iron receiver, fitted with a conical 

 screw-plug and other joints and connections of steel. The action of 

 the pump had been maintained until 25 atmospheres of oxygen had 

 been accumulated, when suddenly this latter part of the apparatus ex- 

 ploded, at the same time diffusing a shower of sparks, reminding one 

 of the phenomena observed when iron or watch-spring was burnt in 

 oxygen. On examining the shattered fragments of the iron receiver, 



V ^5 ^^ , 



it was manifest that this result had indeed happened ; and it appeared 

 that the combustion of iron was possible under the circumstances, a 



