THE COLLAPSIBLE TUBE much to be desired. This, and the toxic dangers associated with it, restrict its use to such things as printing inks, enamel toners, adhesives, rat poisons and the like. It is difficult to get an enamel for it which does not show serious loss of flexibility and adhesion over a period of several months owing to the development of a surface oxide film which is partially absorbed by the layer of enamel and acts as a catalytic "drier." Storage under certain types of atmospheric conditions--proximity to some types of wood will do it--can give rise to a heavy surface deposit which disfigures the shoulder. TIN/LEAD ALLOYS Tubes based upon actual alloys of these two metals as distinct from a plating of tin on a lead core have not achieved any prominence in this country. For a year or two during recent times, a well-known toothpaste was packed in thbes which were made from a 5 per cent tin, 95 per cent lead alloy, but this is the only prominent one which I can recall. On the Continent, alloys such as 48 per cent tin, 3 per cent antimony and 49 per cent lead, and 12 per cent tin, 1 per cent copper, 3 per cent antimony, 84 per cent lead were successfully used for toothpastes. These have a high degree of corrosion resistance and a reasonable appearance. It is my opinion that such alloys would have achieved considerable importance had the competition from the cheap aluminium tube--plain or internally lacquered--been less severe. TIN-PLATED LEAD This is an old favourite, and continues to find a wide variety of uses. It is free from any unpleasant rigidity effects, relatively cheap, and its appearance enables it to masquerade as its tin counterpart until one examines it closely. Normally it consists of a core which contains from 2 to 3 per cent of tin--resulting from the use of plated waste in the melt--with 2 per cent by weight of tin on each side. As manufacturers of tubes it is our job to give the customer what he asks for without asking too many questions. As a chemist, and it is in that role that I appear before you to-night, I suggest that we should look at this system more closely. Even allowing for the difference in specific gravity of the two metals, a tube wall 5 thousands of an inch thick will have a surface layer of tin 0.15 thou. thick. The intending user should bear this fact in mind when assessing its value as protective coating for preventing corrosion. As a barrier between product and metallic lead it is quite effective providing active corrosive tendencies are abse-nt. I prefer to stress its decorative character and leave such matters as the inevitable areas of exposed lead at the end of the nozzle to look after them- selves. 111

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS CORROSION Such is the range of metals at your disposal and only the question of corrosion remains to influence your choice. Each of our C.T.M.A. members is ready to advise and assist in selecting a suitable tube for any given product. More often than not, the time available in which to make a decision is limited and we have established procedures for assessing corrosion behaviour fairly quickly. Even so, let me state quite definitely that there is no real substitute for the ordinary shelf-life test over a period of 6 months, or more, at room temperature. In all other methods an element of risk is present although it gets progressively smaller as our experience accumulates. We are accus- tomed to receiving jars of a given product, and in this connection I would say "Don't be mean" 2 ounces (yes, I have had 2 ounces quite recent]y) comes near to being a waste of time, as it is our practice to fill 4 tubes of each type. Half of the specimens are set aside for storage at room temperature whi]st the remainder go into an incubator controlled at 100 ø F. Already,' two points of some importance have arisen. First, occluded air can play an important part where the product is potentially corrosive. Spooning a product from a jar to a tube, and tapping the latter on a bench to pack it down, is hardly the equivalent of machine-filling from a hopper containing freshly prepared product, often fairly freely-flowing due to being slightly warm. Secondly, this matter of 100 ø F. has to be considered carefully. In my opinion, anything higher is not justified, and any product which suffers considerable change in physical form at 100 ø F., due to emulsion breakdown or melting of its fatty content, from which it does not recover on cooling, should be treated with suspicion, whatever the corrosion result. After three or four weeks at 100 ø F., tubes can be opened and any resulting damage to the metal surface observed. How long does this represent under normal. conditions ? Some say six months, but I think the real answer is that it doesn't represent any particular time at all. Any visible corrosion must mean the rejection of that particular system, though a negative result is notl to be taken as the green light signal to go straight ahead, but as an ambe rl signal to proceed with caution whilst further circumstantial evidence can be::' obtained sufficient to reduce the risk to acceptable proportions. I hav e personally encountered a case where no corrosion resulted during three:! weeks at 100 ø F., but severe pitting corrosion occurred at room temperature!ii after only five weeks. What other steps can be taken if the product must be?•i marketed before the expiry of a proper shelf-life test ? In the first place, individual responsible for formulating the product must make full use of background knowledge concerning the behaviour of similar products ingredients in common with the new one. Actual pH determinations be made, bht their value should not be overrated to the extent of any safe range nonsense. I once encountered an artist's colour which was..11 three-component system, one of which was water and another an 112