EXAMINATION OF THE HETEROGENEITY OF AMORPHOUS SILICO-ALUMINAS AND ALLOPHANES USING THE ELECTRON MICROPROBE

Amorphous silico-aluminas of varying composition prepared by simultaneous precipitation from aluminium nitrate and sodium silicate solutions were found to be heterogeneous by analysis in the electron microprobe. Exceptions were samples of Si/Al atomic ratio 1.5, which showed no heterogeneity for varying conditions of preparation. Silico-aluminas prepared by the co-hydrolysis of ethyl orthosilicate and aluminium isopropoxide were more heterogeneous, and their heterogeneity showed a greater variation with composition. The technique was able to establish heterogeneity of compositions but it was not certain whether homogeneity of the samples in the microprobe represented the homogeneity of composition in view of the large number of particles that appear to make up the aggregates. The most likely explanation of the heterogeneity is thought to be the presence of a matrix of variable composition surrounding the particles. Two out of five natural allophanes showed no evidence of heterogeneity.     

Comparison of bandaging and elevation of the claw for the treatment of foot lameness in dairy cows

Objective
To compare the effectiveness of three treatments for sole injuries in dairy cows and to evaluate the ease and speed of applying the treatments.
Design
A randomised clinical trial.
Procedure
The three forms of treatment were elevating the affected claw of a lame cow with a wooden block glued to the unaffected claw (39 cows), elevating the affected claw with a rubberised shoe glued to the unaffected claw (42 cows) or applying a padded bandage to the whole foot of a lame cow (31 cows).
Results
the percentages of cows that recovered from lameness at 3 and 7 days after treatment were significantly higher for cows treated with wooden blocks (P = 0.013 and P = 0.008) or rubberised shoes (P = 0.026 and P = 0.0003) than padded bandages. Cows treated with blocks had a recovery rate of 48.7% at day three and 65.8% at day seven, and cows treated with rubberised shoes, rates of 45.2% and 76.2%, respectively. Cows which had a bandage applied to the foot had recovery rates of 19.4% at day three and 32.3% at day seven. However, by day 14, there was no significant difference in recovery rate between the three treatments. Rubberised shoes were shown to offer a number of advantages over wooden blocks. The shoes were significantly quicker to attach than blocks (median of 9.5 minutes compared with 14.0 minutes, P < 0.0001) and remained on the claw longer (57.1% of rubberised shoes remained at 30 days compared to 30.8% of blocks, P = 0.025). The rubberised shoes also offered an advantage over wooden blocks for operator safety and health by reduing contact between the potantially hazardous adhesive used to attach both devices and the skin of the person applying the device.
Conclusions
Rubberised shoes are a superior method of elevating an affected claw in conditions of lameness likely to respond to removal of weightbearing forces.     

REACTIONS OF AMMONIA WITH SOIL, III SORPTION OF AQUEOUS NH3 BY HOMOIONIC SOIL CLAYS

Homoionic clay suspensions were equilibrated at 25°C with aqueous NH, (0.01 to 0.30 M) by agitating for several days. Using clays extracted from three different soils, sorption of NH₃, measured by titration, followed the order Na > Ca > NH₄ -clay. The difference in NH₃ sorption between Na-clay and NH₄ -clay was matched by an increase in Na ⁺ ion concentration in the aqueous phase of suspensions of Na-clay treated with NH₃, but there was no such effect with Ca-clay. Sorption of NH₃ on NH₄ -clay in aqueous suspension is considered due to proton donation at sites of pH-dependent charge, and the additional sorption on Na-clay to displacement of Na ⁺ by NH₄⁺ ions. The additional sorption on Ca-clay seems largely due to co-ordination of Ca²⁺ ions with molecular NH. Exchangeable cations affect NH₃ sorption differently when an aqueous phase is present than when dried homoionic materials are treated with NH₃ gas.